Retcon

""Comic book fans will be familiar with the term 'retcon', which in layman's terms means that the writer waves his hand and tells you 'Remember when we said this? We screwed up, forget about that.'""

- Spoony on Highlander II The Sorcerer.

Retroactive Continuity.

Reframing past events to serve a current plot need. When the inserted events work with what was previously stated, it's a Revision; when they outright replace it, it's a Rewrite. The ideal retcon clarifies a question alluded to without adding excessive new questions. In its most basic form, this is any plot point that was not intended from the beginning. The most preferred use is where it contradicts nothing, even though it was changed later on.

While the term comes from comic books, dating to All-Star Squadron #18 in 1983 and shortened to "retcon" by the end of the decade, the technique is much older. Often, it's used to serve a new plot by changing its context; however, it's also done when the creators are caught writing a story that violates continuity and isn't very plausible.

In Marvel Comics, the person who pointed out the problem and at the same time provided a plausible explanation was awarded a Genuine Marvel Comics No-Prize by editor Stan Lee, a tradition that was kept alive by other editors after he became publisher.

See also Ass Pull, which is something that was not properly set up before it is sprung on the audience. It is related to Deus Ex Machina. Some but not all retcons are Ass Pulls, and a good retcon can actually improve the current narrative. A good way to get away with a retcon is to reveal new implications or motivations for events that have already been established.

Smoother retcons won't be distinguishable as such, and can even make what was initially an Ass Pull later look like everything was Just As Planned. (In other words, No Prize it into plausibility and away from the dizzying realm of the Ass Pull.)

The retcon is considered by many to occur when current events contradict the past continuity of the series and is evidence of a Writer on Board. Perhaps more often, the retcon does not actually violate Canon, but rather violates Fanon, the set of unstated interpretations usually made by the audience. (An interpretation violated this way is said to be Jossed.) Most competent writers achieve a retcon by relying on a less-obvious but still perfectly valid interpretation of what was previously seen.

As the number of twists and misdirections in a story becomes higher, it becomes more difficult to tell whether an event actually is a retcon (which implies that the writers changed their minds), or a misdirection (which implies that the writers intended the "retconned" version all along, and had been deliberately misleading the audience before). In some cases, it is impossible to tell, short of reading the author's mind. (Even then, it might not helped, as it's entirely possible for an author to be on the fence about what they're planning to do.) As if the issue wasn't muddled enough, you always can rely on Fan Dumb to either claim that mutually exclusive variations are one and the same or repeatedly call "retcon" every single case when one character said something that contradicts claims of another character or presumably objective narration.

A retcon may be used as part of an Armed with Canon campaign launched by one author against the work of another author in the same Shared Universe. Over-use of retcons can result in Continuity Snarl. It can also result in your readers and fans approaching the work with a certain degree of skepticism, cynicism or even complete disinterest, especially if you tend to obviously and quickly retcon away that which turns out to be unpopular or drastically challenges or changes the status quo - after all, why get involved in your latest Crisis Crossover Event which promises to Change Everything Forever and that Nothing Will Be The Same Again if there's a good chance it'll all just be Ret Conned away after a short period of time?

This happens very easily with prequels when the writers aren't being very careful.

Compare Flip-Flop of God. Tends to come in The Reveal format. May involve Opening a Can of Clones. Can at times also qualify as a Throw It In.

Specific variants:
 * Cerebus Retcon: Sometimes a result of Cerebus Syndrome that makes a past event more serious as part of a shift to drama.
 * Revision: A continuity alteration that doesn't directly contradict any previous material.
 * Rewrite: A Retcon that openly overwrites the facts of the previous continuity.
 * Cosmic Retcon: An in-story event alters reality, which results in a Retcon.
 * Remember the New Guy?: A new character is introduced, but is Ret Conned to have been part of the story all along.

Related concepts for explaining away retcons can include the Hand Wave or Lampshading.

Anime and Manga

 * Mahou Sensei Negima will forever hold the record for the fastest retcon ever thanks to the power of fanservice. In the last page of chapter 238, Makie shows up with her friends in kid form, looking smaller than Negi. In the first page of the next chapter, in the very same scene, she is now in teenage form and Marshmallows Negi.
 * So that happened in two weeks worth of real time (or however long it takes between manga chapters), 1 page's worth of manga time, and zero in-universe time. Wow!
 * Somewhere between volume 5 and 11 of the English-language Great Teacher Onizuka manga, the average age of the protagonist's class gets bumped from 14 to 16.
 * The Gundam canon has a pretty significant number of these, but an extremely notable one is the Biosensor from Zeta Gundam. Said to be a device that somehow increases a mobile suit's power based on the pilot's Newtype abilities, the original series events that are attributed to this system are actually far more supernatural in nature. The Zeta Gundam and ZZ Gundam both have the apparent ability to channel the souls of the dead, as well as the pilot's own fury, to increase the power of the unit. The Biosystem explanation may have been added to keep the show closer to a Real Robot style of show, while still allowing these scenes to be unaffected.
 * A bigger example would be the resolution of the series itself in the final Compilation Movie, which not only changed the ending from a Downer Ending into a Bittersweet Ending, but also potentially alters the course of two related sequels drastically (if not does away with them entirely). Yoshiyuki Tomino, who created Gundam and directed the Zeta movies in specific, has said that he considers the movies an Alternate Reality, but many fans like to believe that the movies shift the less-popular Gundam ZZ into Canon Discontinuity territory.
 * Another rather famous example is Gundam Wing: Endless Waltz, which quietly replaces the TV series' Gundams (designed by Gundam veteran Kunio Okawara) with sleeker designs by Hajime Katoki via a Flash Back prologue. Fandom is split on the issue, and there's quite a bit of feuding over which designs are superior.
 * One of the most infamous Ret Cons in Gundam history was the end of the Gundam SEED Special Edition. A scene specifically put in to reinforce a main character's death was edited out to enable an exceedingly unlikely comeback.
 * One episode of Digimon Adventure 02 has a flashback of the season one characters giving up their ability to evolve past a certain level (and by extension, their ability to be of any use in a fight). This comes up right in the middle of the season, soon after the Applied Phlebotinum the now-reformed Ken was using to obstruct their evolution is destroyed, and basically comes across as a cheap excuse to keep the old characters out of the Competence Zone.
 * It also gave Patamon and Gatomon (two heroes from 01 that made the main cast in 02) a reason to DNA digivolve.
 * Ayumu and Hinagiku in Hayate the Combat Butler knew each other in the first season (well enough for them to travel to the Parthenon together), but in the second season, they acted as if they'd never met. However, this may be because the show switched animation studios in between seasons. The second season is following the manga more closely.
 * Also, season 2 began with one. In the end of season 1, it's stated that Hayate's been their butler for over a year, whereas in the first episode of season 2, Klaus says Hayate's only been their butler for a month.
 * This all could be explained by the fact that the events of the last episode of the first anime series (Ayumu and Hina's parthenon trip and Hayate and Nagi's trip to the Aegean sea) were, in the original manga, side-stories that took place during the golden week holidays and that were out of sync with the rest of the series' continuity.
 * Also Hinagiku somehow has her 16th birthday twice. Of course, the one in the second anime was the canon manga version.
 * Some chapters of Bleach contradict Big Bad Aizen Sousuke's description of past events:
 * says that Kisuke Urahara . In the Turn Back the Pendulum chapters, on the other hand, As this comes in the middle of a speech boasting about how evil he is and, there's no reason why he'd be lying, either. Some fans, however, have shrugged this discrepancy off as   being the official reason for his exile, giving Aizen an excuse to not mention.
 * Grimmjow's fraccions were mentioned by Aizen to be mere Gillians after some of them gave significant trouble to Ikkaku, Renji, and Hitsugaya, all of whom can use bankai. Later on during Grimmjow's flashback; however, only one of them is shown as a Gillian while the rest are all in the middle stage called Adjuchas. Seeing as the "stronger than captains" claim about Vasto Lordes and the Gillian statement came in the same arc, it seems as though Kubo originally envisioned the top tier Arrancar to be much stronger than they turned out to be.
 * Some character designs have been retconned, and not because of Art Evolution. Compare Ulquiorra ch. 190 to Ulquiorra ch. 341, where is Hollow hole moved from his throat to his upper chest. Nnoitra's zanpakuto magically became smaller and longer. Santa Teresa ch. 261 and Santa Teresa ch.286.
 * In a similar vein, compare Las Noches before to how it has appeared more recently. Granted it WAS a rather long period of time since he had to do a shot of it, but there's no reason he couldn't reference it first. There's no explanation for the lower level and the absolutely massive towers around the perimeter of the place to be missing at all.
 * Now the villain of the recent arc can literally do this to people's lives. In fact, the only reason he was the main villain is because the real Big Bad wanted to be retconned into a good guy as part of his Evil Plan.
 * In the third Megami sound stage of Magical Girl Lyrical Nanoha, Hayate says that Fate is more of a sister to Vivio, and Nanoha says that while Fate loves Vivio, she is keeping some distance from her. In ViVid, Vivio says she still considers both of them her mothers, and Fate once refers to herself in the third person as "Fate-mama" while talking to Vivio.
 * In earlier manga chapters of Naruto, Gaara had triple-pierced ears despite his automatic sand shield, which (almost always) prevents him from taking physical damage.
 * The existance of the nine bijuu. During the chuunin exam arc, Shukaku was stated to have been a wind spirit and the soul of a mad priest, as well as not even being hinted as having any relation to Kyuubi. Hell, Kyuubi was described as a unique entity in the first chapter whose presence was described to have been like a minor apocalypse, not one of nine creatures that the Shodai gave away as gifts to other villages for 'joining the ninja village club'.
 * Many manga, due to the grind of making deadlines, have minor changes between the magazine versions and the collected volumes, whether due to mistakes being made or the mangaka just deciding things work better when done a slightly different way. Mahou Sensei Negima, due to its intricate storyline and use of various foreign languages, probably has more than most. One particular example is that the posted "birthdate" of the title character changed from the fairly vague "Summer 1993" to the even more vague "1994" between the magazine version of Chapter 10 and the publication of Volume 2. This works as a Revision, as it renders Negi's in-story usage of a historical Japanese method of age reckoning correct, but also makes determining his actual age more difficult.
 * The Uchuu Senkan Yamato movie was meant to end the story, so . After fan outcry, the movie was adapted into the second season TV series with a different ending Several movies and a third TV season later, the second movie is just claimed never to have happened.
 * In Eyeshield 21, Agon's hair is a walking retcon. In one flashback to his 10th grade year he had short blonde hair and in another he had incredibly long dreads. In middle school, depending on whose reminiscing, Agon either had short thick dreads, long thick dreads, short thin dreads, or shoulder-length blonde hair.
 * A couple instances in Fairy Tail such as Nirvana, which was initially drawns with 8 legs but suddenly had 6 when the method by which it had to be destroyed was determined. The characters explain this via Shrug of God in the Q&A section afterward. Then there's also, which, considering there was a burial, really can't be explained away.
 * Early on in Soul Eater, Liz Thompson briefly remembers her and Patty's Backstory, saying that her life took a turn for the bizarre on that day that she got high and tried to mug a Shinigami (Kid). A couple dozen chapters later, it's instead revealed that Kid came to New York specifically to recruit the Thompson sisters as his weapons, no mugging involved. They went along for the ride, at least initially, to milk him for all the money and convenience he could provide them, before coming to admire him for real.

Card Games

 * At the end of the Mirrodin novels of the Magic: The Gathering world,  When the plane was rivisited years later in the Scars of Mirrodin block, this was retconned so that

Comic Books
"Beast: That defies all logic!"
 * Any time a comic has on its cover the following phrase: "EVERYTHING YOU KNEW ABOUT [X] IS WRONG!", look out, retcon incoming, full force.
 * So that one of the X-Men wouldn't end up committing Genocide, Jean Grey was rewritten so that she was never Phoenix and she never died on The Moon. It was the Phoenix Force itself, who took on Jean's appearance and memories (Quasi-confirmed in a later issue of What If..? which showed what would have happened if "Jean" had had her powers stripped rather than committing suicide). Has been retconned several times since then, the latest version is that it was Jean on the Moon. How she ended up in Jamaica Bay a few years after that isn't accounted for.
 * Plus becoming Phoenix in the first place was a retcon. Xavier basically went "Oh, she had this powerful other self in her the whole time, that I just sealed away."
 * From an X-Men fan-parody film on Magneto's retcon survival: "No, that was actually Xorn's twin brother possessed by the sentient mold Sublime, pretending to be me, pretending to be Xorn." As crazy as that sounds, the parody writer is not making that up.


 * "Hey guys, there was a secret team of X-Men that I, Professor Xavier, sent off to their deaths. I really didn't mention it before because I thought that it would have been far too depressing for you guys, and because I am the biggest bastard on the planet. Now go on out there and save that world that both hates and fears us!" (X-Men: Deadly Genesis seemed like it was designed for the sole purpose of smearing Professor Xavier's reputation.)
 * It should be noted the original story clearly stated the reason why Xavier even decided to gather an all-new team of mutants to rescue the first instead of asking for help from their various superhero allies was that the Living Island was telepathically messing with HIS mind so that he would bring it more food (mutants).
 * Superman: His origin, early years, and powers have been revamped a ridiculous number of times just in "official" comic book continuity (and not counting in-story changes). Probably the most notable and drastic example took place in John Byrne's "Man of Steel," commissioned by DC in the 1980s to "clean up" the past several decades of Superman continuity by revamping his origin and the story of how he began his superhero career. Among other things, this retcon scaled back Superman's powers from the ridiculous levels they had been inflated to (although they have since begun to creep back up a bit), re-established Superman as the only surviving Kryptonian (that one didn't stick either), and wiped out previous continuity in which Clark Kent had a hero career as a teenager in Smallville using the name Superboy, during which time he also befriended the young Lex Luthor.
 * That last retcon is also notable for completely borking the continuity of the Legion of Super-Heroes comic, since the eponymous Legion was introduced in the Silver Age as a group of thirtieth-century teenagers who were inspired to form their own "hero club" by stories of Superboy's exploits. The Legion's writers at the time tried to patch things up by, variously, establishing that Superboy had only existed in a pocket universe, killing off the pocket universe Superboy, revamping one-shot character Mon-El into a Superboy Expy, further rejiggering the timeline by having Mon-El kill the Time Trapper, and finally scrapping and rebooting the whole damn thing during the Zero Hour crossover in 1994.
 * The Legion of Super-Heroes was then rebooted again in 2001, and then retconned again in 2007 back to a variant on the original continuity, with some adjustments. By this point, alternate timelines, retcons, and reboots are a fact of life for Legion fans.
 * Another major Superman retcon that most people don't know about is his attitude. Siegel and Shuster originally wrote him as very rough and aggressive. On one occasion he kidnapped a slumlord, trapped the man in one of his own shoddy buildings, and threatened to collapse the whole structure on top of the guy if he didn't promise to improve conditions for his tenants. He also "accidentally" snapped the neck of a wife beater. A far cry from the Big Blue Boy Scout we all know and love today.
 * Happens even worse to Superman's cousin, Supergirl. Not only have there been four separate versions, but the modern version's history became so convoluted on its own that Sterling Gates just Retconed it out in issue 35, to give her the simple story we all thought was true before.
 * In another notable comic-book retcon, Batman is now known as a superhero who refuses to use a gun or to kill (well, most of the time). This was not true in the first year or so, although he didn't actually kill humans very often and most villains died from Karmic Death. See Pay Evil Unto Evil.
 * Batman has enough to fill the list. One of the most notable concerns events in the story arc Hush. The titular villain appears revealed as, before he turns out to be an imposter (and not the real Hush, at that). Later, a ret con revises the story so that.
 * The Spider-Man stories "One More Day" and "Brand New Day" infamously altered twenty years worth of continuity by erasing Peter Parker and Mary Jane Watson's marriage from continuity. This happened because Spider-Man saved his aunt's life by making a deal with Mephisto, a "demon" character typically used as the Marvel Universe stand-in for the Devil.
 * Not that before was any picnic. Like with JMS's "Spider-Totem" story, implying that there was fate or something profound lingering over Spider-Man's simple origin story.
 * The infamous Clone Saga had to muck around with continuity so much (both because of its initial premise and because of the unholy mess it later became) that at one point they had to dedicate an entire special double-sized issue to retconning away a previous retcon.
 * Back at DC, the revamp of Firestorm in the late '80s when John Ostrander took over. This was the start of the idea of the "Firestorm Matrix," and culminated in the character going from nuclear man to fire elemental. Oh, and by the way, the nuclear power plant explosion that fused Ronnie Raymond and Martin Stein? That was not just fate, not just a coincidence. You see, Stein was singled out to be the "true" Firestorm/Fire Elemental all along!
 * Which led to Ronnie and Mikhail Arkadin leaving the Matrix and Stein entering it to bring Firestorm to his "pure" form to fight the villain Brimstone. Raymond would later return as "classic" Firestorm in the '90s with Stein as Elemental Firestorm as a separate character. Then when Jason Rusch became Firestorm, Stein returned somehow in humanoid form.
 * The fastest turnaround in retcon history may appear in Uncanny X-Men Annual #2. Serving as both a prequel and installment to Dark Reign, it does away with Namor being presented as a skeevy, smelly, creepy old man by turning the dialogue between him and Emma subtly flirtatious. Shame he couldn't do anything about Emma being written as a valley girl.
 * Wolverine's claws originally appeared to be part of his glove, so the revelation that they were part of his body may or may not be considered a retcon. Later X-rays of his arms clearly showed that the claws were implants with mechanical housings and an extension/retraction mechanism. When it was later "revealed" that his claws were a natural part of his skeletal system, the conflict with the earlier x-rays was never mentioned.
 * Similarly, Wolverine's eternal rival Sabertooth first appeared in Iron Fist as a psychopathic human murderer who wore clawed gloves.
 * In his early X-Men appearances, Wolverine's skeleton was said to be reinforced with strips of adamantium. The current incarnation has the adamantium fused throughout his bones at a molecular level.
 * In issue #34 of Deadpool, it is revealed that Deadpool is not actually Wade Wilson, but stole the identity from the man who would become T-Ray. This was later retconned in such a senseless, ham-handed way into a trick by T-Ray to mess with Deadpool's head that most fans didn't even remember it until it was restated in Cable & Deadpool.
 * Despite the fact that Cassandra Cain's entire upbringing was a never ending training from hell, she did love her father, and yet she ran away from him. The reason was that her first kill was the very first time she had witnessed death up close and due to her body reading abilities she thought it to be very, very, scary. Thus she found out her upbringing was evil. Now enter the last issue of Adam Beechen's mini series about her where it is revealed that she hated her dad all along, and that she had actually witnessed her father committing murder up close many times before her first kill.
 * Writers for Fantastic Four initially couldn't decide whether or not the title characters kept their identities secret through Clark Kenting. The retcon was a combination--they thought their identities were secret, and everyone else was humoring them.
 * A rather controversial retcon happened in the Green Lantern series. When DC wanted to reimagine the series, Hal Jordan (the Green Lantern)  After this, Hal was replaced by Kyle Rayner. Kyle brought an upswing in sales for the book for some time, but eventually DC decided to bring Hal back. In order to smooth over his   with fans, it was revealed that
 * This change was also another entry in the long list of retcons of the Green Lantern's "yellow weakness." First, Green Lantern was weak against the color yellow because of a necessary impurity in his power, then it was revealed that the restriction wasn't necessary at all, it was something artificial the Guardians imposed on the Green Lanterns to keep them from going power-crazy. When Kyle became the only Green Lantern, the yellow impurity was removed. In Green Lantern: Rebirth it was retconned so that the yellow impurity was caused by  Since then, the current manifestation of "the yellow impurity" is that the Green Lantern can only use his power against the color yellow if he knows the (most current retconned) source of the yellow impurity, and consciously overcomes his fear.
 * Star Wars: Jedi vs. Sith is basically an official Fix Fic that fits together disparate elements from the Prequel trilogy that conflict with the original trilogy (1,000 years vs. 1,000 generations for the Republic), elements from the Prequel trilogy that conflict with each other, the Valley of the Jedi from Jedi Knight II, some novellas that were in part themselves retcons for the Dark Forces Saga, among other things.
 * A rather controversial retcon by the same author as the Green Lantern example was in The Flash Rebirth. Barry Allen came back (which was fine) but now instead of the previous "Happy Family" he had, his father was accused of the murder of Allen's mother.
 * Another Flash Retcon involved Wally West asking Specter to erase the memories of his identity from everyone on earth after the new Zoom tried to kill his wife. Specter did this but left a loophole so that certain characters would remember everything when Wally took his mask off or put it on in front of them. His wife left him for a while, but came back at the end of the arc. Hilariousinhindsight when you realize it did the same basic thing Brand New Day set out to do (Make their identities secret and make them single, not that the last part was a reason for doing the Flash arc) and did it better.
 * In the Disney Comics, The Phantom Blot's identity was retconned to be a complete mystery, in the first issue he appeared in, not only was his face seen, but his face resembled, arguably, this was a good decision, giving the Blot an air of mystery.
 * Deconstructed in Bates and Weisman's post-Crisis relaunch of Captain Atom for DC, in which the eponymous hero (Anti-Hero? Protagonist?) has one origin, which the military covers up, instead publicizing a "false" origin, which was Cap's pre-Crisis Charlton origin. Later on, when Cap lost his powers temporarily, he wore the costumes that he had worn in the Silver Age, because, after all, the public in-story would be familiar with those costumes, having been told he used to wear them.
 * When the 3.75" G.I. Joe figures first sold, GI Joe was envisaged as an American anti-terrorist task force. When they were made available in the UK, they were sold under the name Action Force. They were accompanied by a comic of the same name which established that Action Force was an international anti-terrorist organisation, of which GI Joe was the name of the American branch.
 * DC's 1991 event Armageddon 2001 turned out to be a huge mess at the end of the day (isn't it always?) and a major source of Character Development for one Hank Hall (Hawk of Hawk and Dove), which continued through Zero Hour until his death in the pages of the 2000s Justice Society of America relaunch. It also had the nasty effect of unceremoniously killing off the second Dove (Dawn Granger) in a cheap shock scene. However in the later pages of JSA, a big retcon by Geoff Johns would unfold: The woman who the JSA thought was a comatose Lyta Hall turned out to actually be Dove disguised by Mordru in some strange concealment spell (apparently they had to retcon Lyta to Dove at the time due to some issue with Vertigo too). Your Mileage May Vary if the retcon was successful or not, as the explanation was quite convoluted and Squick:
 * After her return, Dawn then mysteriously gained a younger sister named Holly, however this change was received even worse due to it contradicting various things in the '80s Hawk and Dove series, including Dawn being an only child and the powers being unable to pass on to anyone else. Unsurprisingly, Holly wound up becoming C-List Fodder down the line as it seems no writer could figure out what exactly to do with her or how to portray her.
 * The Marvel Comics Micronauts were inexplicably brought back to life in a 1996 episode of Cable. This was exactly ten years after they sacrificed themselves to create a Genesis effect that completely restored their ruined Homeworld into a new world at a natural state. In Cable, Homeworld is inhabited by Psycho-Man who is using Baron Karza's old body banks to create dog soldiers.
 * Commander Rann, Mari, and Bug are now the only Micronauts. For licensing reasons, they are now called called The Microns; the others having died in war (Marvel no longer has the license to use Acroyear and most of the others. Huntarr's absence is baffling since he was created by Bill Mantlo, the writer of the first Micronauts series).
 * Homeworld is once again an overpopulated technometropolis and the Microns are freedom fighters. Homeworld is again under the iron fist of someone who probably has to remain unnamed due to licensing restrictions.
 * In a never released story (again due to licensing), Baron Karza and Thanos have a fight which merges all of the Microverses into one ,so now Sub-Atomica and Jarella's Homeword are now in the same dimension.
 * Rann and Mari's appearance and personality are different in every re-appearance. In Cable, Rann is buff and heroic looking while Mari's look screams butch lesbian. And she seemed to have given up the swords for normal futuristic weapons. Then Rann and Mari are looking like their old selves in Captain Marvel, although they don't do much more than talk (kind of like a typical episode of Star Trek TNG). In Realm of Kings: Son of Hulk Rann now sports a goatee and reading glasses. And unlike in Cable where Mari had about three lines between the two issues, she's back to her usual verbose self but now talks like an average Earth bimbo instead of a Homeworld Princess. And look at the man legs on her.
 * Bug is now a member of the Guardians of the Galaxy and for some reason, he's normal human sized and not about 3 inches which is normal when Microversians travel to the regular Earth universe. Rann and Mari (who is once again inexplicably letting others call her Marionnete) have a robot sidekick named Carl (don't ask me) and their latest enemy is Son of Hulk. They journey's around the Microverse aboard the Endeavor III (which sports the most insanely stupidest ship design ever seen in print or screen: a giant atom). It looks as if someone really hated the deeper, more cerebral Micronauts: The New Voyages.
 * At least in the Marvel Universe this kind of things can be easily explained away thanks to their * infinite* number of alternate universes. It is entirely possible that the current Micros are just not the originals and that they're as confused as to whom they're dealing with as the heroes are.
 * Stephanie Brown died at the end of War Games as after she was tortured by BlackMask, Leslie Thompkins withheld vital medical treatment. Her autopsy photos were shown to prove the dangers of crime-fighting to Misfit. Batman never had a memorial case for her because "she was never really a Robin". This wasn't a very popular decision. Except she never died: Leslie faked everything because her secret identity was compromised, her body was switched with an overdose victim with a similar body type, and Batman knew this all along. Here's Shortpacked! on the last one.
 * In the Flemish "De Rode Ridder" series, based on a series of books of the same name, album 131 provided a retcon of the meaning of the title: for about 64 books and 130 comic albums, it had been thought that the title referred to the nickname of Johan the protagonist "The Red Knight", based on his red tunic, 130 revealed that actually Johan was the "Rode" Knight because he belonged to the family of the historical(!) Lords of Rode.
 * Marvel: The Lost Generation is a twelve issue miniseries built entirely around retcon - specifically, filling in the blank in Marvel history from the 1955 to 1961.
 * In the late 90's, when Chris Claremont once more began writing for the X-Men, the character Sage was retconned to being one of Xavier's original students, placed as a spy in the Hellfire Club under Sebastian Shaw.
 * As revealed in the 1980s title Monster Hunters, minor 1940s Marvel speedsters Hurricane and Mercury were both Makkari of The Eternals under assumed names.
 * On the other hand, Agents of Atlas eventually revealed that the Golden Age heroine Venus is, contrary to previous portrayals not the goddess of the same name. Aphrodite was not amused.
 * The French comic series Donjon provides one of the best Retcons ever so far. In the very first issue of this Funny Animal gritty comic, the Dungeon Keeper has a look at a picture of his lost love who looks human. Then, in a prequel album, we see her alive under the traits of a snake. Then the authors showed a portrait painter picturing a bird lady as a human and explaining "it's a style that people like these days".

Film

 * An interesting example occurs in the film version of The Bourne Ultimatum: At the end of The Bourne Supremacy, This exact same scene occurs in the middle of Ultimatum, after we learn
 * This semi-twist has generally been referred to as "awesome" or thereabouts.
 * The Star Wars prequels possibly set the record for biggest number of ret-cons in a major motion picture series in the shortest screen time.
 * In Star Wars Episode VI, Leia tells Luke that she remembers her real mother; however in Episode III, we see that her mother (Padme) dies shortly after giving birth to both twins -- thus either presenting a serious retcon, or else making Leia the most amazing infant-prodigy known in terms of early-childhood memory (particularly since Luke was born first, but remembers nothing).
 * ...In Episode IV, Obi-Wan mentions that Anakin wanted Luke to have his lightsaber when he was old enough. However, unless Obi-Wan heard Anakin screaming something very different than what was said onscreen as he was being roasted alive on the shores of Mustafar, this is altered quite drastically in Episode III. Though some fans shrug it off with it being From a Certain Point of View.
 * ...In Episode VI, Obi-Wan mentions that, when he first met Anakin, he was already a great pilot. But, come Episode I, the story appeared quite differently. Anakin had never so much as touched a ship when Obi-Wan met him and his only vehicle-related experience came from podracing (though piloting those, specially in the Boonta Eve Course, is feat... except Obi-Wan didn't see the race).
 * Leia mentions in her message to Obi-Wan that he served (her) father during the clone wars. Except her father was a Senator by that point, and while Obi-Wan was leading the Republic's armies as a Jedi General, he never was in the service of Bail Organa. He did serve Leia's biological mother as a bodyguard however.
 * This is probably referenced near the end of Episode III, where Bail Organa helps Obi-Wan and Yoda out in their attempts to eliminate the Sith, and later the hiding of the twins.
 * Hell, the original Star Wars trilogy had nearly as many retcons added to it: Vader becoming Luke's father rather than killing Luke's father, Leia becoming Luke's twin sister rather than a completely unrelated princess (and a few years younger than Luke to boot), Owen Lars going from Luke's biological uncle to Ben's brother (in deleted dialogue from ROTJ) to Anakin's stepbrother in the prequels just to name a few. (though all those were offscreen, as George Lucas kept changing his mind while writing)
 * In turn, Star Wars Expanded Universe also features innumerable amount of Retcons. However, they are generally very subtle, used to explain minor discrepancies. Though a few of them are still significant enough to affect ongoing storyline.
 * The Reveal towards the end of Lethal Weapon 2 that the death of Riggs' wife was no accident but rather a botched attempt by the villains to kill Riggs himself back when he with Narcotics working at Long Beach.
 * In Jurassic Park, the T-Rex didn't eat Dr. Grant because it couldn't see nonmoving objects (in the book, this was in fact a result of splicing dinosaur DNA with frog DNA). In the sequel, this was retconned to rather be that Grant's theories on the T-Rex were wrong, and in fact it ignored him because it wasn't hungry.
 * Kopa, Simba and Nala's son mentioned in the storybook The Lion King: Six New Adventures, was ditched and replaced with Kiara in the sequel to The Lion King without explanation.
 * Lampshaded in Misery, where Annie refuses to accept the first draft of Paul's new Misery novel because it contradicts known facts -- and as his "#1 fan" she knows the books better than he does.
 * Hey, remember when Kyle Reece told Sarah Connor that "There is no fate, but what we make?", in the first Terminator movie? Yeah, me neither, but apparently that was the most important thing in the message he was supposed to deliver to her from John Connor in the future, so the second film makes sure to make us remember he said it, as this idea is a big part of the plot of Terminator 2.
 * At the end of Rocky, Apollo Creed tells Rocky that he has no desire for a rematch. Cut to the beginning of Rocky II (which takes place that same night), and Apollo is so desperate for a rematch that he tries to get Rocky to fight him in the middle of the ER they were taken to for treatment.

Literature

 * Discworld, by virtue of being a Long Runner, has a few discrepancies (including when the books actually take place) between the earlier books (such as Wyrd Sisters) and the later ones. Then Terry Pratchett went and Justified it all in Thief of Time by explaining that the history monks just take any time they need and dump any leftover time they have into the ocean. Then there's also the matter of alternate histories. ..
 * Discworld history had
 * In a bizarrely creepy in-universe example, this is actually how the Auditors of Reality COMMUNICATE. They don't talk, they just subtly change the past so that they HAD talked.
 * Somewhat similarly, the Xanth series began addressing early-book continuity issues by saying the magic-dust madness area was spreading and screwing with reality.
 * Several in the Star Trek Novel Verse. A particularly good example: in Star Trek: Vulcans Heart, Romulus' capital was given the name Ki Baratan. It had previously been called Dartha, but that was in a story set a century prior. Later novels used the time gap for a reasonable Retcon: the capital's name changes as new regimes come to power. Now, books set in the 22nd or 23rd centuries use "Dartha", those set in the 24th use "Ki Baratan". The name change is explicitly mentioned in the first Star Trek: Titan novel. Another good example is the Andorian issue. The Andorians were initially portrayed somewhat differently between Star Trek Enterprise and the Star Trek Deep Space Nine relaunch novels, but later books skillfully resolved the seeming contradictions. The various portrayals now add up neatly. Also, in the Star Trek Enterprise Relaunch, the names of Xindi characters are a blend of screen names and those given in early novelizations. For example, the Xindi known as Dolim was named "Guruk" in the first novelization, so in later books his full name is given as "Guruk Dolim".
 * In-verse example: 1984 is hugely based off this trope. Big Brother can rewrite history at will, and the masses have to eat it up. Retconning is done at the Ministry of Truth, the protagonist's main place of work, and mainly consists of editing out people who fell from Big Brother's favor and were "vaporized."
 * In the Honor Harrington series, later books (and short stories, although they are set earlier in the timeline) reveal that Honor is the result of genetic modification that gives her enhanced physical abilities and an increased metabolism. It raises issues about incidents in the early books she's described as accomplishing because of practice, training, and being raised on a higher-gravity world, instead of being inherently stronger and faster.
 * In the first book, when the story of Pavel Young's attempted rape and its aftermath is mentioned, the resulting stomping of said aforementioned rapist-wannabe is given as due to her martial arts training and world of origin. In Field of Dishonor, the winning of the duel is implied to be due to her rage and relentless practice. It's only well into later books that it's revealed she had a tad more of an edge than just the learned skills.
 * Also, David Weber had to retcon the length of ships versus their weight, as he'd initially neglected the Square-Cube law, leaving the smallest warships about right but the biggest ones "not quite as dense as cigar smoke."
 * From the Harry Potter series: in Harry Potter and the Philosophers' Stone, Dumbledore flies to London for a supposed meeting, then flies back, arriving just in time to . We were probably supposed to believe that he was on broomstick. But later books introduce the ideas that wizards have instantaneous methods of travel: Floo Powder, Apparition, etc. Book 5 tells us Dumbledore went on a flying horse (Thestral) because he wanted to arrive late because the Ministry (who were supposed to have called the meeting) were annoying him. But couldn't he have just taken Floo Powder at a later time?
 * In Harry Potter and the Chamber of Secrets, Ginny Weasley is described as having green eyes, but in the seventh book we find out she has brown eyes, the same as her mother.
 * In the first book Rowling had Voldemort tell Harry that his father "put up a courageous fight" before he died, and there was no reason for him to lie to Harry at this point (although it's not inconceivable that he was exaggerating). Seven books on, James Potter is killed in flashback without raising so much as a finger against Voldemort, though James did try to hold him off, but was killed quickly, having forgotten his wand.
 * YMMV considering that means Harry's father took on VOLDEMORT WITHOUT A WAND knowing he would die but that the second it would take to kill him may be the second it would take to save his families life. Many would believe that is damn courageous.
 * Also Rowling made Flint, a character who is said to be in 6th year in the 1st book, remain there in book 3. When asked about this, she said, "Either I made a mistake or he was held back a year. I think I prefer Flint making the mistake." (That is, she's...kinda-admitting?)
 * In an otherwise throwaway line in Quidditch Through the Ages, powerful wizards are said to be able to Apparate across continents. Come Deathly Hallows, however, this is quietly retconned; Apparition is now said to have a range of effectiveness less than that of Western Europe, and even Voldemort is forced to fly "within range" of a certain location before he can Apparate.
 * In The Old Kingdom series the waterfall which separates the first and second precincts of Death is described as "getting louder" when an entity passes through it from the second to the first precinct in Sabriel, but that is retconned in Lirael where an entity passing through causes the waterfall to go silent, and thus agreeing more with the idea that a pathway must be made through the waterfall by magic.
 * A very confusing retcon occurs in regards to "Gore crows", bodies of dead birds reanimated with a single spirit. They are at first described as extremely dangerous due to many of the birds being able to overwhelm an individual, but later when Prince Sam kills one with his slingshot, the Disreputable Dog claims that the other gore crow, which took turns spying on the main party, would be killed because they are both linked to the same spirit. But if this were true, then the first description would not make sense, as as soon as the individual was able to kill one of the crows, the rest would perish.
 * There's a difference between making a part of a soul retreat from a body and banishing it to Death.
 * In the second book, the age of Lirael (the paternal half-sister of Sabriel) is given as a little younger than Elimere (Sabriel's first born daughter) despite the fact that in the first book, Sabriel's father died the very day Sabriel first met the man who later became her husband and the father of both her children. This means Lirael was conceived well after her biological father's death. No frozen sperm or time travel explanations are given in the books.
 * The Lestat that appears in Interview With A Vampire is a rather stupid, petty villain with a streak in banal evil. Anne Rice wrote in her later books that this portrayal was merely Louis' spiteful gossip and/or misunderstandings.
 * If The Vampire Lestat is read before Interview With A Vampire, the impression that Louis is giving the account as a bitter ex-love becomes pretty unmistakable.
 * In the Jurassic Park novel, Ian Malcolm is very definitely dead. They're even trying to get through diplomatic red tape to get him buried. By the time of The Lost World, Malcolm is alive and well, having only been... mostly dead.
 * In Stephen King's Misery, psychotic nurse Annie Wilkes forces Paul Sheldon to retcon the death of Misery Chastain in his series of romance novels. His first attempt is to simply Rewrite it, but he is forced to do a Revision in which Misery was buried alive in a coma when Annie considers the rewrite to be cheating.
 * In the Sherlock Holmes stories, Arthur Conan Doyle originally intended Holmes to die in "The Final Problem" (as the name kinda implies), but the Holmes fans were so furious (there's a story that an old lady screamed "murderer" at him on the street) that in the end Conan Doyle had to Ret Con his hero back to life in "The Adventure of the Empty House". Opinion pretty divided on whether this is a good thing or not: there are some very good Holmes stories after he comes back, but overall the quality does go down, due to Conan Doyle not really caring any more.
 * Len Deighton's Hook Line & Sinker trilogy retconned the events of his earlier Game, Set & Match trilogy. In the latter trilogy, Bernie Samson discovered that . The former trilogy changed this so that
 * The Dragonlance War of Souls trilogy retcons the role of Chaos, "Father of the Gods" to "delusional god who thinks he's father of the gods."
 * Not to mention retconning out the ending of Dragons of Summer Flame. Not only does Tasslehoff not die, but.
 * Officially, there's now another Chaos retcon..
 * Another retcon is the conception of Steel Brightblade, which no character knew about until The Second Generation.
 * Don Quixote. Part 2, which was written a decade after the publication of Part 1, is predicated on the idea that Part 1 was published as non-fiction in his world. This gives the author an opportunity to address contradictions in the original work, by having a character who had read it ask Quixote himself for explanations of what really happened.
 * The actual explanation for this is that there was a unlicensed second part "Second Volume of the Ingenious Gentleman Don Quixote of La Mancha: by the Licenciado (doctorate) Alonso Fernández de Avellaneda, of Tordesillas" written that directly insulted Cervantes. It ended up serving as the impetus for Cervantes' Part 2, and there are many jabs, both direct and indirect, at this spurious sequel, in Cervantes' own sequel.
 * The Hobbit was written well before JRR Tolkien came up with the plot for The Lord of the Rings. In the original story, Gollum's wager for the Riddle Game was a "present", which turned out to be the ring. Once The Lord of the Rings existed, having Gollum ever do anything which might lead to him losing the Ring suddenly made no sense at all, and so that chapter had to be Ret Conned. Tolkien dealt with it by making Bilbo an Unreliable Narrator, and having Gandalf shake the "true" story out of him during The Lord of the Rings.
 * The character of Elrond is also slightly different from one book to the other: when Tolkien wrote The Hobbit, he gave him the name of Elrond, which he had previously used in drafts of The Silmarillion for the son of Eärendil, but did not make him the same character, which is why it isn't clear in The Hobbit whether Elrond is actually counted among Elves - he appears to be a Man. It was only when writing The Lord of the Rings that Tolkien explicitly made the character that appeared in The Hobbit, and the character that appeared in The Silmarillion, one and the same. (Some have argued that this creates another problem, since Elrond, a descendant of Turgon, should perhaps have laid claim to his great-grandfather's sword.)
 * Though not much use a Sword would be to Elrond anyway, and it's likely Elrond figured Gandalf would need it more. At least it explains how Elrond knew what Glamdring was so quickly.
 * The Hobbit was written before Tolkien had even worked out the basics of Middle Earth, so the earliest editions contain things that were later eliminated, like references to policemen.
 * In The Odyssey, there are two sirens. Yet there is art that depicts three. How to fix, how to fix -- obviously, one of them committed suicide in a rage after Jason and the Argonauts! And another one after Odysseus got away! (Which raises the question of how the third one died. . . they never did settle that.) Older Than Feudalism.
 * Arthur C. Clarke's 2001: A Space Odyssey directs the fateful mission to Saturn, but The Film of the Book goes to Jupiter (according to The Other Wiki, because the special effects team couldn't make a satisfactory ring effect for Saturn). When Clarke wrote 2010, he decided that Jupiter worked better for the new plot and went with it.
 * 3001: The Final Odyssey retconned the events of the first 3 books to occur at a later date. 2001 was changed to 2015, with 2010 and 2061 getting a respective forward push, as well. (It was written in 1996, by which time it was pretty clear that Clarke's 2001 would not happen.)
 * Word of God -- erm, I mean word of Deus -- is that each book takes place in a slightly alternate continuity from the others. Which explains Dave/Star Child's Badass Decay between 2010 and 2061, and Floyd not appearing as part of the Dave/HAL/Monolith entity at all in 3001. Some people still find this incredibly lame.
 * Since the Cthulhu Mythos has had so many authors over so many years, lots of stuff gets retconned back and forth. Particularly notable is August Derleth's [oft-reviled attempt to impose Elemental Rock-Paper-Scissors and a good/evil dichotomy on Cosmic Horror and fans revising the wings of Elder Things and Mi-Go (which were originally said to allow them to fly through space) to solar sails.
 * The Sword of Truth series: Presumably to explain the inconsistencies in the timeline generated by the official version of the Magic of Orden, the final book reveals that  So far, so neat and tidy, until you remember that the climax of the first book and a large chunk of the plot of the second book (and, indirectly, most of the rest of the series) rest on  . Not that the logic was entirely convincing to begin with...
 * In Animorphs, Ax is at the beginning unable to communicate in thought-speak while in human form, explained by the fact that humans cannot use thought-speak. Later in the series, Ax repeatedly uses thought-speak while in human morph, due to the fact that it is after all, a morph.
 * In the first book, Jake can communicate in thought-speech with Tobias when he's in a morph, which would have come in really handy for the characters later. K.A. Applegate intended to take that scene out, but forgot.
 * An in-universe example: in The Chronicles of Narnia: Prince Caspian, the "history" under Miraz' rule is described as "more dull than the driest history book you have ever read, and less true than the most exciting adventure story."
 * In a strange retcon of the events of the Trojan War, some poets contend that Helen never actually went to Troy and that Paris instead was tricked into abducting an illusion of her (don't ask). In another retcon, Helen is carried off by Paris but ends up being stranded in Egypt. Euripedes reconciles these two variations in his play Helen. He also rewrote Trojan War history with his Iphigenia plays, crafting a scenario in which she survives the efforts to sacrifice her to the gods and has various misadventures while her father is off to war.
 * The prequels to the Belgariad and Mallorean books do this to several different plot points. The most Egregious example is that taking into account Silk's cameo towards the end of Belgarath the Sorcerer, when he and Garion encounter Asharak in Pawn of Prophecy, Silk should have recognised Asharak on sight, should have known that, and should hence have realised that the fact that Asharak was poking around was highly significant and should be reported to Belgarath immediately. It's handwaved with the implication that Asharak was tampering with his mind, but that still doesn't explain why Belgarath didn't react to the name.

Live Action TV

 * Alias - "Hey you know the man you loved that died and you grieved over? Yeah, know he's alive remember, and we totally knew about it all the time, even though you cried lots in private over his loss."
 * The Star Trek franchise is a Shared Universe spanning more than forty years, with writing of, to put it kindly, variable quality. Naturally, it has had many retcons:
 * The Klingon makeup change was just better budgeting from the show to the movies. Worf's scene in Deep Space Nine in the flashback turned it into an actual plot point.
 * The reference was meant to be a quick joke about the effects budget in an episode that was already tongue in cheek. The writers expressed total bafflement over how much of an uproar it had created with the fandom. Reactions in Usenet newsgroups ranged from "can't you guys relax and take a joke", to "we demand answers NOW!" to "We were fine ignoring it until you morons brought it up". The same lunacy also made another Worf joke from that same episode, the "The Great Klingon Tribble Hunt", official canon. Canon is serious business.
 * In the end, Star Trek Enterprise resolved the matter once and for all, proposing that the change was a side effect to the cure for a fast-spreading plague.
 * The changes we see in Kang, Koloth and Kor are alluded to as well, as the episode ends with a Klingon doctor speculating on the fortune to be made in the reconstructive surgery business -- an option for seasoned veterans who had acquired fame and fortune in their younger days, but probably not for young starship commanders looking to make names for themselves. (And neatly ties up the early version of the Klingon makeup used in Star Trek the Motion Picture as the result of botched reconstructive surgery.)
 * Exactly the same thing happened to the Ferengi between Star Trek the Next Generation and Deep Space Nine, turning from a mighty empire with warships that seriously threatened the Enterprise into a one-note joke race of scheming cowards.
 * TNG's pilot, "Encounter at Farpoint", implied that the Ferengi were known for eating sentient beings. This was never brought up again.
 * Well, even in their debut episode, they were scheming cowards. The I'm a Humanitarian trait was turned into a metaphor for cutthroat economic practice.
 * TNG introduced an entire new race mid-series: the Cardassians. They had never been mentioned before, and yet in their very first episode, it is made clear that the Federation and Cardassians had been at war. And recently enough to be living memory for several crew members. Indeed, the plot of the Cardassian introduction episode is all about the psychological fallout from them. They got a lot of mileage out of this retcon.
 * And then again between TNG and Voyager, the Borg changed from assimilating only technology to being essentially techno-vampires.
 * In the final episode of Star Trek the Original Series, "Turnabout Intruder", Dr. Janice Lester pulls a Grand Theft Me on Kirk to break through the glass ceiling, because even in the utopian future of Star Trek, women were apparently barred from service as starship captains. This embarrassing piece of 1960s male chauvinism was retconned out by attributing it to the delusions of a mentally unstable woman, despite Kirk's explicit on-screen acceptance of both the accuracy of her accusations, and the injustice of the policy.
 * You could argue that Kirk was playing along, having gotten tired of constantly trying to explain the truth to her. Still, that interpretation removes the whole point of the episode. The really tragic thing, though, was it was the last episode of the series. What a way to go out.
 * The revelation made late in Star Trek Deep Space Nine that Dr. Bashir is a genetically engineered superhuman causes numerous conflicts with earlier episodes, and basically makes him an awful person through Fridge Logic. For instance, the episode reveals that he could win every game of darts against O'Brien. Not only does this make their entire friendship seem like a farce, since playing darts is the chief activity they're seen enjoying together, but it contradicts the episode "Visionary" where O'Brien's foreknowledge of where Bashir's darts are going to hit was used to show that he had really been to the future. Then the episode "Distant Voices" is centered around an alien probing his mind and drawing out his deepest secrets, but him knowing himself to be the product of illegal genetic engineering never comes up.
 * Star Trek the Next Generation has a revelation that excessive warp speeds are causing holes in spacetime (in an Anvilicious Aesop about pollution and the environment), which prompts the Federation to limit ships to Warp 5. Characters in a couple of subsequent episodes pay lip service to the "speed limit" right before they break it, but after that it is forgotten completely, with the general Fan Wank being that an improved version of the Warp Drive that didn't mess up subspace was invented. May also apply to what ought to be the inevitable ramifications of a new technology or application thereof, such as retrieving a heretofore-disintegrated crew member out of the pattern buffers of the transporter.
 * In Peter David's Star Trek: New Frontier novels, there's an offhand reference from a character who can "see" spacetime about the damage still being done by warp travel. Of course, David loves tossing in little offhand references to all sorts of things from Star Trek history that pretty much all other writers (and fans) ignore, sometimes preferring to forget.
 * This got so noted that fanfiction writers No-Prized it, coming up with the dual ideas of the ruts worn in spactime healing over a period of time and simply changing your routes to avoid cumulative Spatial Fatigue.
 * In Star Trek Voyager, The Mole Seska claimed to Chakotay that she impregnated herself by stealing his DNA. She also told Kazon leader Cullah, who she was sleeping with, that the baby was his. After the baby was born and was clearly a Cardassian/human hybrid with no Kazon-like features, Cullah was naturally pretty pissed off, which led us into the season ending cliffhanger. However, between seasons everyone decided that the Kazon weren't up to the job of being the show's big recurring bad guys they were envisioned as, much like the Ferengi on TNG, so they decided to drop them from the show entirely. This involved Seska dying, and Cullah running away with the baby. Naturally, fans wouldn't accept Chakotay's kid being raised by the Kazon, however unwillingly he fathered it, so just before this the Doctor reveals it is actually Cullah's baby after all. The baby's appearance is Handwaved by saying there's never been a Cardassian/Kazon hybrid before so before now no one knew what one would look like, and it'll probably develop Kazon features as it ages.
 * The two-part Star Trek Voyager episode, "Year Of Hell", plays retconning literally. the Big Bad has developed a weapon that lets him use retcons to change the timeline (while he himself is protected by Applied Phlebotinum). He first uses it to reverse a stunning defeat to his species... Only to discover he's accidentally retconned his beloved wife and daughter out of existence. He keeps trying. (Also provides a handy Reset Button: evidently, destroying his ship undoes all his Ret Cons... And Ramming Always Works.)
 * And then there's the question of currency, specifically whether the Federation uses any during the 23rd century. There is at least one mention of a crewmember "earning their pay" in a TOS episode, though that might have only been a colloquialism Kirk was using. In "The Trouble with Tribbles", we see what clearly looks like trade with a human salesman - it's hard to imagine that guy was just in the business of giving away these critters for free. Then by The Voyage Home Kirk has a quote about people in the 20th century "still using money", implying that they don't anymore. You might think that they stopped using money at some point between TOS and the fourth movie, but the tone and reactions in the scene seem to indicate the Enterprise crew is completely unfamiliar with the concept of currency - so the change wouldn't have occurred in their lifetime. And of course, by the TNG era, they pretty much beat us over the head with the fact that the Federation doesn't use money anymore (except for outside trades with other species, especially the Ferengi). Enterprise seems to hint that currency was abandoned when the Federation was first formed, a few years after the end of that series, but it's very vague about it. And then, to add further confusion, the 2009 movie has a scene that takes place in a bar, on Earth, that clearly seems to operate on capitalistic principles (not to mention the Nokia phone in Kirk's uncle's car). Now, that movie takes place in an alternate timeline, but since the two timelines diverged on the day of Kirk's birth, it would mean that even in the original one, currency was still legal tender at least until that day. To sum it up, it seems like we're now just meant to vaguely accept that they've phased money out by the 24th century without asking too many questions about how they did it or the precise moment when they did.
 * Tongue-in-cheek Word of God suggests that Nokia and Budweiser have been nationalised.
 * Fairly easy to Hand Wave by pointing out that the existence of replicators and holographic crew members likely indicates a post-scarcity economy -- any currency that would be used in one would likely have next to nothing in common with currency as we understand it today.
 * Trills make their first appearance in an episode of Star Trek the Next Generation ("The Host"). Here, the symbiont clearly has total control over the host body and considers transporters to be harmful. In Star Trek Deep Space Nine, the makeup is completely different, the host and symbiont create a combined personality, and use of transporters does not appear to be an issue.
 * Nobody knows that trills are a joined species, even though Dax must've gone through Starfleet Academy years before, and that wasn't treated like it was unusual. (Dax was never called 'the only Trill in Starfleet'.)
 * Dallas is the most Egregious retcon in 20th century American entertainment - in order to bring a character Back From the Dead, it made an entire season All Just a Dream. You'd think a Soap Opera, of all things, could figure out an easier way to bring someone back.
 * Although Scrubs doesn't usually do a lot of continuity, one of the later episodes has a throwaway joke where J.D.'s friends claim that he cannot see women wearing their wedding ring. If that is the case, how was he able to see Carla in the later half of the show (5-9), or T.C.W., for that matter...
 * Another J.D.-related retcon is that in later season of Scrubs, he says he doesn't like beer. In the earlier seasons of Scrubs, however, he's clearly shown drinking beer in some episodes.
 * Several in the reimagined Battlestar Galactica Reimagined:
 * In the initial mini-series and first few episodes, humanoid Cylons are shown to have glowing spines during intercourse. However, this was officially retconned by producers when it was pointed out that Dr. Baltar already had an amazing Cylon detector. In his pants. Though note Scifi Channel commercials for the second half of season 2, which show a spinally-luminated fetus. Also, in the commentary for the most recent webisodes, writer Jane Espenson mentions it was planned to depict Eight's spine glowing during sex with  but the scene was rewritten for them to kiss instead. The novelization of the Miniseries says the glow isn't visible to the naked eye, but that book isn't Canon.
 * In early episodes we learn that human Cylons had 'evolved' from the Centurions after the First Cylon War. Later there are a few hints that human models already existed before the war. Then, in the last ten episodes, it is revealed that
 * Several characters are revealed to be Cylons  after they and the audience thought for years they were human.
 * In the miniseries, the audience learns that there are only twelve Cylon models that look like humans. These are gradually revealed over the series, the twelfth and final Cylon in "Sometimes A Great Notion".
 * This one is especially bad because
 * In My Parents Are Aliens an episode showing how the aliens met the children shows that Brian and Sophie originally had disguises resembling the presenters of Crimewatch before changing into their familiar forms. Later in the series 7 finale they said that they stole the identities from the children's real uncle and aunt, also named Brian and Sophie.
 * Doctor Who: Many of the most notable features of the series, such as regeneration and the Time Lords, were retconned in, often to account for some out-of-character problem.
 * Two of the more specific cases of retconning in the original series, the second of which is also a case of Continuity Porn:
 * In "The Sea Devils," the Doctor points out that the cave creatures from "Doctor Who and the Silurians" should have, in fact, been named the "Eocenes" instead of the "Silurians," because of the epoch they originated from, which is the real-life author (same for both stories) correcting his earlier mistake when he was called on it after the broadcast of the first story.
 * In "The Arc of Infinity," one of the Doctor's companions asked why weapons were recently able to be fired inside the console room, when (as mentioned in "The Hand of Fear," six years prior) it is said to exist in "a state of temporal grace" to prevent such things from happening. The Doctor shrugs it off as just another part of the ship that happens to be in a state of disrepair.
 * Time Travel used as a plot device already allows a significant amount of retcons to be added simply with a hand wave, but the master stroke has to be the Time War. Since it's stated to have taken place sometime at the end of the Eighth Doctor's lifespan, it never has to be shown on-screen, yet can be used as an excuse to justify almost anything. The later developments with the universe being destroyed (and rebuilt again) at the end of Series Five (with the Pandorica) are even better, as literally EVERY continuity error in the entire series, right from the time of the First Doctor, can be dismissed using this as an explanation. Seriously, the Pandorica has become the ultimate retcon for Doctor Who...
 * Also, the doctor was originally supposed to have 13 lives, but it seems that will change...
 * Season 2 of Heroes has a rather clumsy example. In the middle of the first season, it's revealed that Matt's wife is pregnant. This causes a few fans to wonder if the baby is really his, since she cheated on him earlier in the season. However, in an episode set five years in the future, we learn that the kid is named after Matt, sends him crayon drawings of himself and mommy from hiding, and, most tellingly in a show where almost everyone with superpowers gets them from Superpowerful Genetics, has a power. Then in an early Season 2 episode, Matt says that whoops, turns out it wasn't his kid after all. In "Fight or Flight," a later Season 2 episode, however, it is implied that he has accepted that it isn't his child without any actual proof, when he has a nightmare in which his wife chastises him for not reading her mind and learning the truth, so this may be a reversion more than rewrite.
 * In S1, Mohinder was originally said to have been two years old when his sister died, but they changed it so that he was born months before she died in order to wrestle Molly into his plotline.
 * Season 3 retcons Sylar's murderous ways as a side effect of his original ability. His ability to know how things work apparently gave him a "hunger" to kill people just so he can satisfy his fix for more power. This of course ignores that S1 and S2 showed him utterly reveling in murder, even when he didn't have any abilities.
 * Although it does explain why a socially suave murderer capable of killing someone, turning around and dropping back into whatever character he was playing to manipulate someone else into doing what he wanted without missing a beat would have a Room Full of Crazy stating "Please Forgive Me" over and over, which Suresh encountered in S1.
 * The writers have a go at fixing this one again, with Sylar shown to have gone through a guilt ridden phase around the time the series began, presumably redecorating appropriately.
 * Take it as a retcon or a further loss of his humanity, but as of season four Sylar can seemingly suppress his hunger (evidenced by a casual road trip that lasted for several episodes next to tasty brain Luke) but still revels in his murderous behavior, perhaps moreso.
 * The plot that tried to explain this retcon also retconned Elle's background, as she is portrayed as relatively normal and even caring and guilt-ridden, rather than sociopathic and murderous as in season 2. This contradicts season 2, in which she states she was diagnosed as a sociopath at eight.
 * The first one noted above was settled once and for all in volume 4, where it's confirmed that the baby is Matt's.
 * It seems that every other episode that something new is added to Noah Bennet's back story that wasn't there before. A prime example in season 4 when we see that Noah almost participated in an affair during the events of season 1, when his daughter was in danger. Then later in the season, we find out that he had a deceased wife that had never, ever been mentioned in the plot before.
 * Claire having magic blood in Series 2 which can resurrect anyone from the dead, such as when Noah Bennet was killed after being shot in the eye. This is promptly forgotten after this incident and by Series 4, when her biological father Nathan is killed, reviving him in this way is never an option.
 * The actual cause of what gives them powers has also been retconned several times. At first its hinted at being a genetic trait which has something to do with the brain. This made some semblance of sense, until an Eclipse somehow turned everyone's power off. And then Hiro's mother had some kind of mystical power that was the key to abilities... or something?
 * Buffy the Vampire Slayer plays with and subverts this trope in a very interesting way within the show. In the end of the first episode of season 5, Buffy suddenly has a sister that has never appeared or been mentioned before, and it had previously been established that Buffy is the only child. But neither Buffy nor anyone else shows any signs that anything is out of the ordinary. It later turns out that powerful magic was involved that not only created Dawn, but also retconned her entire past life into the memories of the people of Sunnydale. Even when it turns out she didn't really exist until some months ago, she continues with her current life as if she were a regular person.
 * In season 1, Giles states that he is inexperienced with magic and has never used it before. By season 2 it has been established that while he was in college he was using magic recklessly enough to gain the nickname "Ripper" and to summon a dangerous demon that killed several other people.
 * Also done well in Spike's introduction. He expresses anger that Angel has gone good, saying, "You were my sire, my Yoda, man!" Angel doesn't elaborate on this at the time. Later we learn that it was Drusilla who actually turned Spike into a vampire while Angelus was his teacher and role model. In another episode Spike outright says, "Drusilla may have made me a vampire, but you made me a monster."
 * Also done in the episode with Jonathan. He's retconned into the intro where all the focus is on him and it's an AU where everyone looks up to him and he's famous and successful. Only for one episode, though.
 * Both Spike and Angel had their ages changed. For Spike it happened twice. He went from "barely 200" in School Hard, to 126 in The Initiative, to 120 in Fool for Love. Angel had 29 years added to his age in the episode Becoming.
 * A minor example concerning Anya's demon friend Halfrek. She was played by Kali Rocha who had appeared in another episode as Cecily, one of Spike's human love interests. In her next episode when she and Spike appeared on screen together they had Halfrek say "William?" and then the two avoided each other's gaze, implying Halfrek and Cecily to be the same person. Also Halfrek's flashback scene in "Selfless" was changed from the Renaissance to the Russian Revolution to support this.
 * Smallville: The most Egregious example of this was a vital clue hidden in a stained-glass window that hadn't been there in the previous episode, as well as the same window had been destroyed several times over the course of the series. The ridiculousness of retconning a window a week after it had last been seen casts a shadow on what would have been otherwise well-written.
 * The original meteor shower that brought Clark to Earth now includes Davis 'Doomsday' Bloom several feet away. Lionel's agents manage to reach Davis after the Kents have already carried Clark home.
 * The show introduced a major character from the comics, Jimmy Olsen, in S6. He had a supporting role for the next three years, then they decided to kill him off in the season finale. To keep the show in line with the comics, they had his funeral reveal that his name is actually Henry James Olsen, and it was implied that his previously unheard of little brother was the real Jimmy Olsen. Three years' worth of retcon!
 * Which brings it closer to the comics (with Jimmy Olsen being much younger than Clark Kent). Also, Superman's pal is no longer one of his villains' identical twin brother. (Actors-wise, that is.)
 * In Friends, Ross is shown in later episodes as having a long standing passion for dinosaurs, that stretches back to childhood. However, in the first season, he states he only picked paleontology as his major on a dare.
 * Friends did this more and more with each flashback, resulting in the internal history making little sense. In the first episode, Rachel backs out of her wedding and we find out she hasn't seen Monica or Ross in a very long time. None of the other characters recognize her, but importantly, Chandler doesn't. But in Season 3, we find out that Chandler actually met Rachel just a year before her wedding day, and actually wanted to sleep with her. We then later find out that they met even earlier than that when Rachel was still in High School. This means that when Rachel met Chandler briefly in the Season 3 flashback, she didn't recognize him, or she didn't want her friends to know she knew him.
 * Friends was notoriously bad at doing more harm than good with their retconning, as the episode The One Where Chandler Can't Cry goes to show. The entire premise of the episode was (in typical Friends fashion) exactly what it said on the tin. Only, Chandler was easily the most emotional of the boys, and had several earlier episodes revolving around this fact.
 * He had the same thing happen with his sudden and crippling fear of dogs.
 * The same episode that introduced Chandler's dog phobia also reveals that Ross hates ice cream... despite the fact that a past episode (The One After the Super Bowl) shows him just fine with eating it.
 * Also, in "The One With the Prom Video", it's clear that Chandler had never seen Fat Monica or pre-nose job Rachel, but in a later episode he was retconned into meeting them.
 * The most painful, quickest retcon ever was in The 4400. One episode revolves around re-opening the 4400 center. Notably, police try to stop it and tell Shawn he can't heal anyone, because no one can use 4400 abilities, whether they were a 4400 or got it via promicin injection. The very next episode features someone saying "Maia is a 4400, she can legally use her ability". The show then kept on like that without even acknowledging that superhuman abilities were entirely banned in the first few episodes of its last season.
 * The Zat stungun in Stargate SG-1 used to be able to disintegrate people and things. They don't do that anymore, because it was getting entirely too silly.
 * This is referenced in episode 100 Wormhole X-treme, where upon suggesting their equivalence of the Zat gun be allowed to dissolve a legion of alien corpses, the idea is denounced as stupid.
 * Not to mention the show retconning a number of things from the original movie, despite the movie itself still being mostly canon: Ra wasn't the last of his species, the Goa'uld didn't look like Protoss with mouths, Abydos isn't "on the other side of the known universe"... Even happened with minor details like an extra "l" being added to O'Neill's name and Sha'uri inexplicably becoming Sha're.
 * The most plot-significant one being the symbols on each gate are the same exept for one (the symbol designating the gate's point of origin), so they don't have to spend half of every episode figuring out the return address like they did in the movie.
 * Hell, about ignoring the whole different language issues that were such a big part of the plot of the movie, and now the Stargate acts like a Universal Translator for some reason. Now it's so much easier to have alien cultures magically speaking English.
 * Jack' O'Neil in the movie was a tough as nails, Death Seeker utterly depressed and full of anguish and anger over his son's suicide. Now his son is only mentioned in passing as just having 'died' (no mention of his suicide), and now Jack is a character full of optimistic spirits and cracking jokes every chance he gets.
 * Later episodes establish that Jack's son got into his gun cabinet and was killed when a gun discharged in his hands, which caused Jack significant angst and drove a wedge between him and his wife.
 * Mid third season of Stargate Atlantis shows the first shot of the interstellar gate bridge. The first episode of season four shows its completion. Watch carefully in this scene. At one point, we see Carter moving past a computer with a wire frame of a Stargate, notably looking like it has an iris on it. Fastforward to episode seventeen where an entirely brand new line is added into the "previously on" segment, where McKay claims there is actually no need for the midway gates to have irises at all. This change is made for no reason other than to have an episode where the Wraith board the midway station and destroy it. The fallout of this episode is that the I.O.A refuses to build another because they're afraid of the same tactic. The possibility of building another and just adding irises is convieniently never brought up, so it would appear this retcon was all for the sake of justifying the permanent removal of a quick way back to Earth from the series.
 * A cross-series Retcon occurred between Cheers and Frasier. In a late Cheers episode, Frasier remarks that his father is dead and was a scientist in life, two things that are clearly not true in Frasier - it was explained as being the result of Frasier and Martin's relationship being quite cold at the time.
 * In "Night Court", Brent Spiner played a character named Bob Wheeler from West Virginia. After a number of people from that state complained it was later revealed he and his family had actually come from Yugoslavia.
 * The series long neural-clone subplot in Farscape hadn't actually been thought of when Harvey first appears in "Crackers Don't Matter". The writers needed to think of a way to have Scorpius appear more frequently without losing his menace in the process, so decided to have him pop up as an offkilter hallucination. It worked so well, they ran with it and started dropping hints something more was going on inside Crichton's noggin, before introducing Harvey proper later in the same season.
 * Car 54 Where Are You? broke continuity to suit the backstory of the episode probably more than any other sitcom.
 * Red Dwarf is full of retcons. Major examples include the number of the ship's original crew being raised from 169 to 1169 (and raised to 11169 in the books), Lister having his appendix removed twice and Lister's relationship with Kochanski being altered from simply someone Lister was interested in but never asked out to ex girlfriend.
 * The Kochanski contradiction can be explained because she came from a parallel universe where she had a relationship with Dave Lister (this much is canon). Since our universe's Lister wants to get together with her, he pretends he had a past relationship with his universe's Kochanski in an attempt to bring them closer (this is fan speculation).
 * Angel had one about halfway through season four when the gang find out that Big Bad Jasmine had engineered most of the major events that brought the gang together.
 * Highlander is full of retcons between the films and the series. One huge example is Connor's fight with {{Film/{Highlander}} The Kurgan}}. The series retconned it to simply being a really big quickening from a normal battle rather than The Prize.
 * Power Rangers Ninja Storm originally indicated that it wasn't part of previous Power Rangers continuity, but their team-up with Power Rangers Dino Thunder shoved it back in.
 * Mighty Morphin Power Rangers has one when it came replacing Rangers. In season 2 when Jason, Trini, and Zack had to leave the team needed to acquire a special sword to transfer their powers to Rocky, Aisha, and Adam, but in the following season when Kimberly need to give her powers to Kat she was handed her power coin away.
 * Spooks the main arc of Season 9 qualifies (it qualifies as other nasty tropes too)
 * Prison Break did this with alarming frequency, to the point that they actually resurrected a character whose DECAPITATED HEAD WAS SHOWN ONSCREEN.
 * That 70s Show does this with with a very early character, Donna's younger sister Tina. She appears in just one scene of one episode (Season 1 Episode 5) and is never heard from again. She is mentioned just once afterward in Season 2 Episode 6, in a joking lampshade at the end by a soap-style announcer: "And whatever happened to Midge's daughter Tina? [...] Confused? You won't be, after the next episode of That '70s Show!"
 * Supernatural's Trickster secretly being Archangel Gabriel. At the time of his creation in the second season, angels weren't even planned to appear in the show -That decision was made during the third season, due to the Writer's Strike cutting the season short. Then in the fifth season they're revealed to have been the same being all along. Whether it was a good Retcon or not is hotly debated by fans of the show.
 * Good Times: The 1976-1977 season finale saw Florida marry an elderly gentleman named Carl Dixon and the two moving to Arizona (to tend to Carl's frail health condition); this was done to explain Esther Rolle's departure from the cast. When she agreed to return at the beginning of the 1978-1979 season, one of her demands was -- and it was granted -- that no mention of Carl ever be made, not even why he was no longer in Florida's life. (Rolle, whose Florida character was a devout Christian, said she did not want her character associated with a hardcore atheist.) Although fans often speculated about Carl's departure (death, a particularly acrimonious divorce, etc.), no mention about the Carl-Florida relationship or its end was ever made.
 * The Brady Bunch: Events and characters that occurred in the Brady Spin-Off The Brady Bunch Variety Hour are retconned by the time The Brady Brides make it to air; as such, none of the events in the ill-fated variety series are considered canon.
 * The MTV Reality Show The Hills was a major offender when it came to this. During the pre-credits voiceovers, new dialogue and/or footage would be added to address what the episode's focus would be, even if it conflicted with events as they were seen in previous episodes. These included, but were not limited to, pleasant conversations between characters being reframed to look more antagonistic, characters describing events that never could have occurred within the timeframe of the show, extra dialogue being looped into conversations (said when the camera isn't on them) to change the focus of the plot, and deleted footage that showed characters doing activities that they were never seen to have done in the previous episode. This fed a lot of fan speculation as to whether or not the show was scripted.
 * Monk has had a couple involving Trudy's death. First, it's originally stated that Monk was there by Trudy's side as she died from the car bomb, but later episodes show he was across town. Additionally, Monk originally did not know that the reason she'd left that fateful day was to pick up medication for his brother Ambrose, and Ambrose personally blamed himself for her death as he felt that if she hadn't done so than maybe she'd still be alive. However, in a flashback to the day of her death in the series finale she specifically tells Monk she's picking up Ambrose's medication.
 * Additionally, in one episode as part of a gang of Chinese criminals' plan to lead him to Monk, they attempt to trick him with fortune cookies. One of the fortunes states that he will receive money from an uncle, which Randy rebukes since he only has two aunts and no uncles whatsoever (it was actually referring to tax return money, the uncle in question being "Uncle Sam.") Two seasons later, another episode is kick-started with the death of Randy's uncle. Not only that, but Randy visited his farm several times as a kid.

Professional Wrestling

 * Due to its inherient nature, professional wrestling is full of retcons. This is especially true for angles (storylines) that flop or otherwise fail to resonate with the audience. In the years before the word gained negative political connotations, the terms "abort" and "abortion" were used in carny language to reference a suddenly-ended failed angle.
 * TNA did an extended storyline where Sting turned heel after Hulk Hogan and Eric Bischoff came on board. Hogan was clearly acting as a face, while it was hinted Bischoff might be working behind his back. However, Sting was a heel and was attacking faces. He made some vague comments about people not understanding, but he was a heel. Lo and behold, Hogan & Bischoff cheat TNA president Dixie Carter out of controlling interest in the company. As a result, Hogan and Sting's heel/face alignments are retroactively reversed.

Tabletop Games
"Holden Shearer: They're very rare, they live in the cracks of the setting and perform their feats in dark times people strive to forget. But they're not new, as the GS Ps are new; thus, 'they were always there.'"
 * Magic: The Gathering has "The Revision". In the early days, the novels and comics were done by different companies than the card game itself, but when Wizards of the Coast became a bigger company they wanted to publish their own books. Reading the 10 books and the pile of comics so far was apparently too much effort for them though, so they issued a statement that everything that had come before was still valid, unless new stories contradicted them, thus creating what fans call "prerevisionist" and "revisionist" continuity. Several books were actually published that replaced older comics.
 * Warhammer 40000 has undergone quite a few of these through its four editions, including entire races being retconned out. Anyone younger than 20 remember the Squats? Didn't think so.
 * The official policy on the Squats now appears to be that the entire race was murderlised by one of the Tyranid Hive Fleets. The Tyranids are God's gift to retconners. "Hey, what happened to those guys?" "Eaten by Tyranids."
 * Similarily, the Fimirs of Warhammer. Originally created to be the "iconic monsters" of the Warhammer world, they are now remembered only by people who played Hero Quest early in the nineties. Their reproductive cycle revolved around capturing human slaves for brides, which probably made for some thorny conversations with the parents of younger gamers. The Tyranids probably got them too, somehow.
 * Apparently they're back in the Storm of Magic expansion.
 * In Exalted, the Sidereal Exalted (who are basically Fate Ninjas) have a panic button called Avoidance Kata. Its effect? Retcon the whole world so that they made a different choice several minutes ago and are anywhere but here.
 * Word of God on the recently introduced Liminal Exalted is that they've been there for a long time, we just didn't notice them.


 * Unknown Armies gives us Entropomancers (chaos mages who get power from taking risks), who are based around re-writing history. Cliomancers, despite being history buffs, can only affect people's PERCEPTION of history, as well as their memories. Of course, this still counts as retcon.
 * The "Luck" advantage in GURPS can have the enhancement "Wishing" added to it which allows the person using it to retcon a recent mistake into whatever result they like.
 * The writers have also retconned the weights a melee weapons as including the sheath in order to bring them down to reasonable levels.
 * Wizards of the Coast wielded a + 5 Rethammer in the Fourth Edition Forgotten Realms. Virtually every pantheon was either wiped out or retconned into one or more existing (usually human-ish) gods, along with the vast majority of the other minor gods. The previous planet of Abeir-Toril was changed to two separate worlds. Also gone is the Blood War, a massive near-eternal war between the devils of the Nine Hells and the demons for the Abyss for ultimate badassery.
 * They do give a reason why there is no Blood War. Asmodeus, the lord of the Devils, became a god and took a third option, by kicking the Abyss out of the way so they don't have to fight it.
 * A relatively minor, but still noticeable one was made to the war between the Gods and the Primordials. Originally, the Gods defeated the Primordials and banished them to the Elemental Chaos. Recently, however, it was "revealed" that a third party, the Primal Spirits, intervened and ordered a truce. Granted, it's not as bad as some of the other retcons 4th Edition has brought, but still...
 * And of course: Mystra dies. Again. This is what, the third or fourth time? What makes this time so special?
 * In the early days of the storyline collectible card game Legend of the Five Rings, a number of card typos brought about story retcons. The most consequential of these was an oni card misprinted with the name of the hero Hida Yakamo. This led to a story point about Yakamo selling the oni his name, heavily influencing his character development and in the end being explained as the general model for oni-human interaction in Rokugan.
 * An actual rule of the universe in Nobilis: if you cause a car to fall apart, reality will insert a history of mechanical failures to explain that.

Video Games
"Sora: You mean...
 * In the original Kingdom Hearts game, Ansem, the leader of Hollow Bastion, was said to be a once-benevolent king who became obsessed with the study of darkness and was eventually consumed by it. In the second game, however,.
 * Team Sora's reaction when Mickey explains this to them is pretty much what most people are thinking:

(long silence)

Team Sora, in unison: WHHHHAAAAAATTTTTT?????"

"Liquid: The price of physical prodigy... Few more years and you’ll be another dead clone of the old man. Our raw materials are vintage, brother. Big Boss was in his late fifties when they created his copies."
 * Hell, the existence of the Nobodies as a whole is a retcon. Originally, when a person succumbed to the darkness in their heart, the darkness consumed it entirely, leaving them with no heart, thus, a Heartless. However, starting in Final Mix, it suggests that the Heartless is the heart, and the body becomes something else.
 * Xehanort gets several even crazier retcons in Birth By Sleep. Let's see...
 * Halo series. From the first game we are given: "You are the Master Chief, born for battle, bred for war, you are the last of Spartan-II project. Your brethren have died". First novel clearly shows they were just missing in action in the fog of war, novel three brings them back entirely. The games never reference any of this.
 * Halo: Reach heavily retcons Eric Nylund's The Fall of Reach, which described the origins and early years of the SPARTAN-II program, as well as the Fall of Reach. In the novel, the Pillar of Autumn is already on its way out of the system when the Covenant attack on August 30, 2552. The ship turns back and the Spartans split up; the Master Chief leading a small team to destroy a ONI Prowler's NAV Computer (In accordance with the Cole Protocol, all vessels are to destroy their navigational databases upon contact with the Covenant, lest they discover the location of Earth.); the rest head to the surface to defend the generators powering the orbital MAC Cannons, the only thing keeping the Covenant from achieving victory. By the time the Chief completes his mission, the generators have fallen, a ground invasion is underway and the Covenant have control of orbit. Left with no alternative, the Chief heads back to the Autumn which flees the system. Rather than plotting a blind path (Again, the Cole Protocol), Cortana uses data from a Forerunner crystal to plot a course to Halo. The first game's plot follows. Halo Reach, meanwhile, Cue massive Fan Dumb / Fan Wank.
 * In the beginning, it was established that the all the Forerunners went extinct after activating the Halo Array.
 * Albert Wesker in the original Resident Evil was a stock horror film character, the obligatory traitor who gets killed at the end. Realizing that the series was in need of a main villain, they brought back Wesker from the dead in Resident Evil Code Veronica and released a fictional documentary called Wesker's Report which explained that Wesker was behind the events of Resident Evil 2 and Resident Evil 3 Nemesis as well.
 * In the original PlayStation version of Resident Evil, the severed hand founded by Joseph Frost at the beginning of the game was originally established to be that of Edward Dewey's, Bravo Team's originally unseen pilot. When both, the remake and Zero came out, Edward Dewey was established to had died earlier during the events of Zero and the corpse found by Joseph now belongs to Kevin Dooley, a helicopter pilot who accompanied Bravo Team on their mission.
 * Originally, the team wielded generic Beretta handguns in the PlayStation version of the first game. Resident Evil 3 Nemesis then introduced the Samurai Edge, a customized Beretta that was planned to be adopted as the standard-issue sidearm by S.T.A.R.S. before they disbanded. In the GameCube version, the S.T.A.R.S. members now wield Samurai Edge guns instead.
 * Starcraft Brood War: In the original game, the Terrans are portrayed as a near-offshoot of humanity long isolated from Earth, with a separate historical and technological development. The swift arrival of a United Earth Directorate with similar technology and language in the Expansion Pack manages to contradict the spirit of this several times over. The manual tries to Hand Wave it away with references to bugs built into Terran equipment (and the U E D is the in-game explanation for several new units and technologies) but even a rather lenient interpretation of events has trouble making it all fit together.
 * The (flimsy) justification given out by Blizzard was that the expedition mostly used captured equipment from the Terrans. Alternatively, since the UED is a largely unified state that doesn't appear to have experienced real conflict in centuries in-universe, they may simply not have the capabilities and equipment to fight a large-scale interstellar conflict.
 * One that actually makes sense was a change with the Xelnaga, the race that created the Zerg and the Protess, and were supposedly wiped out by the Zerg before the Zerg even had any of the fighting creatures from the games. With how advanced the Xelnaga were supposed to be, that was a bit of hard of believe, which Blizzard apparently realized so they plan on having the Xelnaga in Starcraft 2, saying they weren't completely wiped out.
 * Before the changes wrought by the novels and Starcraft II, the Xel'Naga were described as a peaceful, benevolent race that engineered planets for sentient life, and were almost wholly surprised by the Zerg attack. They likely had few weapons.
 * Speaking of Starcraft, Starcraft II had a pretty big one involving the Zerg Overmind. In the original game, the instruction manual states that the Overmind was created with an imperative to absorb creatures into the Swarm and thereby improve the Zerg. This is what caused it to rebel and overrun the Xel'Naga. SC 2 states that another force interfered with the creation of the Overmind, enslaving it to that imperative. It also says that the creation of Infested Kerrigan and the death of the Overmind was all part of a Thanatos Gambit to free the Zerg from this control. Kerrigan wouldn't have his imperative. So after creating her, he then went to the most powerful species in the sector, set up camp on the homeworld, and gave them both a reason and the opportunity to kill him. This also conveniently explains why in SC1, the Overmind decided to leave the all-important Kerrigan behind when he went to Auir.
 * Rivaling the Klingons are the orcs from Blizzard's Warcraft franchise. In the first two games the orcs were simply Always Chaotic Evil, but in the third game they were now led by Thrall, a young Shaman, who wants to return his people back to the way they were before the Burning Legion came to Draenor. It turns out that, instead of being bloodthirsty idiots for 100 years as originally stated, they were a peaceful race of warriors who had been corrupted by the Burning Legion only about 5 years before they came to Azeroth. This meant that several orcs remember the time before the corruption. To help with the retcon Blizzard has made a book explaining the corruption and has planned two new books that will show what really happened during the Tides of Darkness and Beyond the Dark Portal video games.
 * To Blizzard's credit, though, they have admitted that gameplay and balance FAR supersede continuity in the context of how important they are, and that if they can't make a game element fit within the confines of the established lore, they WILL alter it to suit their needs. Adding in a dash of Unreliable Narrator (given that all of the tie-in-books and game-based-lore are, in some form, intended to have been documented by those present for those given events) also helps explain inconsistencies, using a Watsonian explanation for certain elements.
 * Even when one allows for Fanon, it's often argued that the draenei are an even bigger retcon than the orcs. In the first two games, they were presumed to be an extinct race. But some survivors (ugly raptor-footed Mooks) appeared in the third game. Then, when the Alliance needed a new race in World of Warcraft, the draenei were picked...and their appearance was changed to make them look like smaller, bluer eredar (big demons who had been heavily involved in the corruption of a titan and were the main villains of the third game). The explanation was that the eredar from the third game are actually the man'ari eredar, a corrupted form of the original Eredar, who were actually the draenei. No one's quite sure what corrupted the titan in the first place (dreadlords were definitely involved, but it seems unlikely that it was them alone), but he was the one who corrupted the eredar, rather than the other way around. The draenei in the third game were revealed to have been mutated by demonic magic. In other words, the draenei the players play are the original unmutated draenei, who are in fact the original uncorrupted eredar. Does your head hurt yet?
 * Let's not forget their Horde counterpart, the Blood Elves. Supposedly they all followed Kael'Thas into the Outlands, but in World of Warcraft, there are a lot of them left in Azeroth, and not only that, they also managed to rebuild half of their capital city in a mere four years. And seeing as there are two banks and auction houses in it, business is obviously going great.
 * That one was actually covered in expanded universe material to an extent; the rpg books that came out shortly after WC 3 explained, in a fairly minor retcon, that while most of the elves in Quel'Thalas and Silvermoon were slain, the city itself was largely left in tact. The main problem was that it was still invested not only with zombies, but with the ghosts of the citizens slain there. The rpg also mentions some blood elves coming back to Azeroth prior to TBC, though not as many as depicted in WoW.
 * Though the RPG also introduced even more retcons into the Blood Elves' backstory, by having them be a minority of the high elves rather than all of them, having drained demons before meeting Illidan, having night elves attack them on sight and having them be nomadic.
 * Also see Not Quite Dead and Staying Alive for mind-boggling character revivals in the game universe. Blizzard heavily retcons everything to make new quests (the Black and Blue Dragons were originally stated to have only the aspects left), and make some playable units (see blood elves and draenei). The fans have just learned to accept it.
 * Not all fans...
 * A rather nasty example comes from the plotline regarding Arthas in Wrath of the Lich King. A plot twist occurs in the Icecrown Citadel instances stating that However, this directly contradicts earlier quest chains which establish that  It also causes even more problems when you consider the fact that
 * It's basically implied that if there's no Lich King in charge of the Scourge, Yogg-Saron would take over, power them up with Lovecraftian eldritch powers or whatever, and have them kill everything.
 * Worgen: Barely sentient ravening extradimensional hellhounds, or just ?
 * A main one, and one everyone seems to forget is that Deathwing, the Big Bad in Cataclysm was killed in the canon campaign of Beyond the Dark Portal in Warcraft 2. Handwaved by Blizzard that he faked his death by crashing into the ocean.
 * The Balrons in the Ultima series were originally the barely disguised Expy of Balrogs from The Lord of the Rings, very powerful and very evil demon lords. Ultima 6 later explains that no, they were actually a misunderstood race of Gargoyles. Interestingly, the existence of demonic Balrons seems to have returned in Ultima Online.
 * Also, near the end of Ultima VI, you are told how you defeated the bosses of the three first games. These retellings remove many of the sillier elements, such as flying an X-Wing in Ultima 1.
 * In The Elder Scrolls RPG series the Imperial Province (Cyrodiil) was always described as being covered in a thick jungle. In the only game that takes place there the jungle has turned into generic fantasy forests and meadows. The explanation for this: A god made the land colder for some soldiers who were too hot and the jungle vanished.
 * The first 2 games, as well as the spinoff Battlespire, mention that there is no race native from the Imperial Province, that the province is a cosmopolitan mish-mash of all the other races. The Imperial line is supposed to be Nords. Then comes Morrowind, introducing the Imperial race, and retconning them as a descendant of the original Nord caucasian race, from which the modern Nords, Bretons (via mix with elves) and imperials are all descended from. The retcon does maintain that the Emperor's family has more Nord blood then most Imperials.
 * One could say that most of the convoluted lore concerning the Elder Scrolls universe is the result of a massive retcon to make all of the possible endings of Daggerfall canon. At the same time.
 * Final Fantasy VII has the "Compilation" cheerfully retconning quite a good deal of the original game's backstory, to the consternation of many fans and the relief of others. For a sample of the changes, take a deeeeeep breath: Crisis Core retcons orchestrated the Nibelheim incident (though it seems to have gotten far more out of hand than he intended), and . Before Crisis forever cements, as well as adds a different incarnation of AVALANCHE that existed before Barrett founded his group, making them behind many events that occured prior to the original game; Advent Children itself changes the personalities of many characters, but especially ; and Dirge of Cerberus retconned considerable amounts of , making HIM more mopey, and added  where there were none before).
 * is explained in a blink-and-you'll-miss-it-moment:  Naturally, Cloud is able to resist it long enough to maintain his Badass-edness, but it isn't until  that he actually stops being mopey and truly becomes his Badass Super Soldier self.
 * Interestingly, some of the retcon in the compilation has already been hit by the Reset Button, as aspects of the Nibelheim Incident changed in the anime short Last Order were retconned in Crisis Core to be more similar to the original game's events.
 * Word of God has stepped in to say that all depictions of the Nibelheim incident represent a different character's perspective and memory of it; bits and pieces of each recollection collectively form what truly happened.
 * Sonic the Hedgehog's retcons are confusing at best. Shadow's dead, no he's not, he's alive, except he's a robot (revealed in the same game where's he found to be alive), except he's not a robot, he's a clone, except he's not, he's really the original Shadow. A retcon so bad it took two games to sort it out.
 * Then there's the entire re-imagining that everything post-Sonic Adventure has brought, with some characters gaining a year, some characters becoming four years older and and one losing ten years. One only has to look at the Archie Comics version of Sonic to see how much of an effect this has had on the early stories.
 * To officially summarize the Shadow Retcon:
 * Team Fortress 2 has had a few retcons since the developers have tried to add more back story to an otherwise plotless game.
 * The back story of the Demoman originally told of him killing his first set of adoptive parents while trying to blow Nessie out of the water, then growing up in a foster home afterward. However, when a comic from the WAR! update in December 2009 depicted the Demoman talking to his real mother (who, in turn, talked about is real father), Valve retconned that the Demoman's biological parents later heard of his great skills at explosives and took him out of the foster home for proper training.
 * And now, the Demoman's eye story gets changed yet again, this time his eye was possessed by MONOCULUS! in the Bombinomicon (Halloween 2011) comic. It isn't known if it's the same Demoman, or if the RED and BLU ones have different back stories with the same result.
 * The Street Fighter series had its fair share of retcons, but some of them are not actual legitimate changes to the story so much as they are actually the result of inconsistent translations between the Japanese and English versions of the game (such as the revelation in Super SF II that Cammy was M. Bison's lover in the past, which never actually occurred in the Japanese ending). One legitimate retcon concerns the many ways Guile's combat buddy Charlie has been killed off throughout Alpha series (stabbed in the back in the first Alpha, gunned down in Alpha 2, and died in an explosion in Guile's ending in Alpha 3). The early anime trailers for the console version of Street Fighter IV implied that Charlie may not be dead after all, but Guile's prologue and ending in Super Street Fighter IV seems to suggest that Charlie is dead again.
 * The biggest Retcon, however, is saved for Gouken, the original master who trained Ryu and Ken. While Gouken's origins, identity, and even existence remained ambiguous for much of the franchise's early years, slowly the character began to emerge and was portrayed as the long-dead (and inherently mystical and mysterious) master killed by his brother, Akuma. Then suddenly in Street Fighter IV, the character's back story was blatantly Retconned to add in the convenient fact that Gouken was never killed, just rendered in a coma and everyone (Ryu, Ken, Akuma, etc.) thought he'd been dead all this time. Admittedly, Gouken was included in the game almost solely as a nod toward the infamous Sheng Long "secret" but nonexistent character in the Street Fighter series, as well as rumors throughout several games that Gouken was somehow playable. Still, this massive Retcon removed most all of Gouken's mysterious, mystical nature and turned him into a standard, more generic fighter.
 * Your mileage may vary. This trope thought it only added to Gouken's mystique to have him show up after something on the order of ten years, alive and apparently well despite having been successfully attacked by what is supposed to be an inherently fatal technique.
 * Do we even need to get started on the Myst series? First, Revelation changed the entire concept of trap books by turning them into prison ages instead and having Sirrus and Achenar return. It also introduced Yeesha, who later on in Uru and even End of Ages bent so many of the rules of Writing Ages that she practically threw both canon and fanon out the window.
 * Uru at least acknowledged that what Yeesha could do was out of the ordinary ("I could write things they never thought possible"). Myst IV on the other hand seemed to act as if the prison books had always been that way which just doesn't make sense.
 * In fact, Uru (and later Myst V) attempted to explain away all the "inconsistencies" of the first four games in a rather interesting way- they are, by Uru canon, JUST VIDEO GAMES. Yeah, it makes sense, but still seems like a slap in the face to some fans of the first (and arguably best) games.
 * The Metroid remake, Zero Mission, contains a great many retcons to the original story, most along the lines of what happens to Samus after she defeats Mother Brain. However, things such as Kraid and Ridley getting massive growth spurts (to match their portrayals in later games) are clearly Rewrite territory.
 * In Metroid Prime, there was a Chozo barrier around the Impact Crater, which stopped the Space Pirates from getting inside, where Metroid Prime (the creature) was. However, in the first US version of the game, Pirate logs indicate that they captured and studies the creature before it escaped. This was very quickly retconned when they realised it was impossible - in the normal English version and the Player's Choice versions of the games, the Pirate logs only say that they know there is a creature there, but they don't know what it is.
 * However, even in the non-US versions, Metroid Prime's scan data says it has mechanical weapons, which (in the US version) it assimilated when the Space Pirates were experimenting on it. Either way, it's still a Plot Hole.
 * Ironically, the original US version would be easier to retcon, as one of the logs from the Chozo mentions that the Space Pirates arrived slightly before the Chozo all died off - so they could have put up the barrier after the Space Pirates discovered it.
 * In Summoner, Laharah is an evil goddess, and her followers, the Nuvasarim, feed on agony. This is thoroughly - and convincingly - retconned in the sequel, in which Laharah is the protagonist.
 * Dark Reign has an ingenious version of this: the first twelve missions are recreations of famous battles between the Freedom Guard and the Imperium. You choose which site to fight for, but the historical results of the battle will not necessarily match your victory. The final mission involves going back in time and retconning history itself by saving Togra and defeating both sides. Thus, the ret con is part of the plot.
 * In Backyard Skateboarding, the playable characters have allegedly never heard of several neighborhood kids. This would fit in continuity for Andy MacDonald, but not for the Backyard Kids because they played in the same league as them for a few years! In MANY different sports! (It may be that Skateboarding is supposed to be from Andy MacDonald's perspective, with the others as just playable.)
 * Metal Gear Solid 3 Snake Eater made a few changes to Big Boss' initially established back-story from previous games. Originally, Big Boss was stated to be born around the 1920's, meaning that he was in his 50's when Solid Snake was born during the 1970's and over 70 when Solid Snake (supposedly) killed him in Metal Gear 2, which was set in 1999. However, he's only in his 30's in Metal Gear Solid 3, which is set in 1964, meaning that he was de-aged by roughly ten years. Likewise, Big Boss' bio in the Metal Gear 2 manual stated Big Boss lost his eye during the 1980's, a few decades later from the events of Metal Gear Solid 3 (where Big Boss loses said eye during an interrogation session).
 * A line of dialogue in Metal Gear Solid Peace Walker places Big Boss's age at 39 years old in 1974, which is jarring when you consider that Les Enfants Terribles occurred only two years earlier and Liquid's dialogue in Metal Gear Solid 2 Sons of Liberty:


 * Who said he was referring to Les Enfant Terribles? He could have actually been referring to the Genome Soldiers? This is also supported by the line being retained in the Collection, where it also included Peace Walker.
 * The eponymous walking nuclear tank itself has had its history changed as well. The TX-55 Metal Gear from the first MSX game in the series was originally the first of its kind, until RAXA and the ICBMG (both from MPO), as well as Metal Gear Zeke from Metal Gear Solid Peace Walker, revealed that there were at least three models before it (technically four, if one counts the eponymous weapon in Peace Walker as a Metal Gear).
 * Well, technically, going by the Graninian definition, Metal Gear ZEKE was the first true Metal Gear. The ICBMG and RAXA were quadrupedic, and Granin's specifications for Metal Gear specifically state that it is required to be bipedal. Plus, although they have legs, it's also debatable if the ICBMG could even walk, even with Ghost's statements of Metal Gear, as RAXA, even when Ursula was able to use it beyond its capabilities with her psychic powers, doesn't seem to actually use the legs to move, or heck, use them for anything else than landing gear. Peace Walker, a weapon even further closer to Granin's designs, also utilized Quadrupedalization as it's primary locomotion ability, going by its full power mode in the game.
 * Gray Fox's back-story was also heavily retconned in MPO. In MG2, Gray Fox reveals during his death scene that he was a half-white war orphan from Vietnam who was adopted by Big Boss after the war was over (which would have been after 1975) and later served Renamo (the Mozambican National Resistance) during the Mozambican Civil War. In MPO, we find out he was a German-speaking child soldier from Mozambique who fought for the Frelimo (who were the enemies of the real life Renamo) in 1966 (four years before MPO and nine years before the Vietnam War ended). The Metal Gear Solid 4 Database doesn't even mention Gray Fox's time in Vietnam, nor his time serving Renamo.
 * The identities of the Patriots have been changed multiple times since the first mention of the organization. In MGS2 they were suggested to be both an Illuminati-like secret council composed mainly of twelve members known as the Wisemen's Committee. The timeline in the ending of MGS3 stated that the Patriots were actually the US branch of the Philosophers, which was the real Illuminati-like organization. But then MGS4 established that was really a cover for their true origins (MPO having previously revealed that the US Philosophers were murdered by Ocelot under orders from Zero) as a different group founded by Big Boss and his team from MGS3 as a sort of continuation of the Philosophers, which Big Boss left over a dispute with Zero, and which Zero passed on to a group of AIs; and that furthermore, Donald Anderson from MGS1 was really Sigint, and Dr. Clark (who revived Gray Fox as a cyborg) was Para-Medic, and that their "accidental" deaths (Anderson's from being tortured by Ocelot, Clark's from Fox's rampage) had been orchestrated by Eva and Ocelot from the get-go as part of their plan to destroy the Patriots and rescue Big Boss. And the really weird thing is, after playing all the games all of the above will make perfect sense.
 * Peace Walker retcons both, Snake Eater and Portable Ops, by revealing that
 * A lot of the plotpoints from Metal Gear 2: Solid Snake were retconned as early as Metal Gear Solid. For instance, Metal Gear 2: Solid Snake heavily implies in both its intro and the instruction manual that the entire world was actually disarming its nukes and the only intact nukes were procured by Zanzibar Land by raiding nuclear outposts. However, Metal Gear Solid retcons this by exposing that more than 20,000 nukes still exist in the world either by 1998 or 2003, despite their goal being to get rid of them by 2001 or 2007, as well as the fact that they were creating nukes, and that START II, which was stated to have not only been ratified, but also implemented long before the events of Metal Gear 2, was mentioned to have not even been ratified yet by the time of Metal Gear Solid. There's also the infamous implication of Big Boss stating that he is Snake's father in Zanzibar Land.
 * In Silent Hill, The exact nature of Silent Hill changes dramatically between games, comics and the film. Silent Hill 1, Origins and the film imply, or outright show that the fog-world and otherworld are caused by Alessa, in retribution for the crimes committed against her. This changes in Silent Hill 2, and is featured in some the comics, which suggests that the town was always a dark place, and that Alessa just caused the evil it to break through into our world. It switches again in Silent Hill 3 and Homecoming, both feature the fog world being caused by the Order, and that they are able to control it to some degree. Other comics say it was caused by the impregnation of a woman by Whately, who does not appear or is mentioned in any of the games. Finally,
 * The first few .hack// games avoided this by being a direct sequel to the anime .hack//Sign; on the other hand, Roots contradict various aspects of the G.U. games (both were released about the same time, but when Roots reenacted some of G.U.'s scenes, the first game was already available for months). The most jarring ones:
 * Shino's death scene (in this case, the retcon was caused by the games). While the scene is essentially the same in both versions, some minor details were changed to contribute to the drama of in the games. Shino got lines when in the anime she didn't say anything, among other changes (such as Haseo not calling her on her phone). Shino's outfit coloring also suffered, as in some of the game's flashbacks it would be black (that is, post-Ovan-disappearance) when, according to the plot, it should be white.
 * Champions Online seems to be lampooning the trope: "Retcon" was their custom term for a respec, until some players got confused by it!
 * Some (minor and easily handwaved) details from the first Jak and Daxter game don't exactly mesh with revelations made in the later games.
 * In the Ace Attorney series, one of the first game's major plot points was that However, according to case 1-5, . Some fans did not take kindly to this, claiming it rendered a good portion of Edgeworth's Character Development in the first game moot.
 * In Pokemon Red, Blue, and Yellow, as well as Pokemon Fire Red and Leaf Green, Giovanni vowed to make amends for his actions, feeling he betrayed his followers and renouncing Team Rocket for good. However, an event in Heart Gold and Soul Silver reveals that Giovanni had in fact planned for Team Rocket to be revived, that he wasn't truly remorseful for betraying them, and the only reason he left was to get stronger.
 * Also, in Gold and Silver, Steel- and Dark-types were stated to be new types. This was omitted in the remakes, owing to the fact that the previous games, even Fire Red and Leaf Green, also had Steel- and Dark-types.
 * Herman Toothrot is a loony eccentric in the first two Monkey Island games. In subsequent games he is inexplicably identified as the grandfather of Guybrush's love interest Elaine Marley. This contradicts a large chunk of the established story, and much shoehorning has to be made.
 * The Legacy of Kain series pulls an interesting in-game example:
 * Guile, a character that the player can recruit in Chrono Cross, was actually meant to be Magus from the previous game. The developers said that they eliminated his backstory because of time constraints and because they didn't want any of the "secondary" characters to have more importance than the others, but evidence still exists that the two were originally meant to be the same person (they both hover instead of walking, have long white hair, and use Shadow magic; Guile's Japanese name, Alfador, is the same name that the child Magus gave to his cat in Chrono Trigger). Surprisingly, in the Updated Rerelease of Chrono Trigger for the Nintendo DS, they retconned the whole story by having Magus lose all of his memories in a canonical ending, thus strongly implying that Guile is an amnesiac Magus.
 * The same thing can be said about Dalton. In Chrono Trigger he was a joke villain, but in one of the bonus dungeons of the DS version you can fight him and discover that . Of course, Chrono Cross tells us that
 * Left 4 Dead went through this a few times. During the development of the game, each campaign was supposed to continue in sequence in the storyline, but play testers complained that they felt it was too much of a downer to see the survivors get rescued and wind up having it fail, starting the next campaign. Valve then made it where each campaign is a separate story. Fans then started to complain that the campaigns felt too out of place, so Valve made the Crash Course campaign that tied in between No Mercy and Death Toll. Possibly due to Fan Wank, Valve made the sequel have the campaigns be all connected in sequence and it was met with positive reaction. In response to this, The Sacrifice comic goes to state that the survivors from the first game have, in fact, gone through several rescues in each campaign one by one (No Mercy, Death Toll, Dead Air, and then Blood Harvest).
 * Raiden's story in the first Mortal Kombat title was much more self-serving, as he had been invited by Shang Tsung to compete and does so in order to prove mortals are puny when matched with a god. His ending from that game has him overthrow the tournament and turn it into a showcase of the gods (that eventually destroy the world). Later games throw this characterization out the window and instead portray him as a concerned protector who feels he must participate in order to avert disaster (as this happens after the first movie also changed the entire story of the first game).
 * Kabal from Mortal Kombat 3 was given the same treatment. The third game presented him as a reformed gangster seeking revenge for the deaths of his comrades  Fast-forward to Mortal Kombat Deception, and
 * Big Bad Natla from the original Tomb Raider had her motives change slightly in the remake. In the original version, . In the remake,

Web Comics

 * The king of all retcons is Sonichu. The creator was trolled by people pretending to be Shigeru Miyamoto, who was talking to the creator, Chris, about a game development. When this troll said that would be impossible to make a game based of fanwork, another troll, posing as a lawyer pretending to be Jay-Z, advised Chris to change several aspects of the comic. What followed were so many terrible retcons, there's a whole Wiki about it.
 * The wierdest part is that the creator actually believed he was in contact with ShigeruMiyamoto and Jay Z the entire time.
 * Xawu retconed a typo that was pointed out on the coments.
 * Several characters in Ctrl+Alt+Del were retconned, even having their bios deleted on the site. Though at first it looks like they were just Put on a Bus or Brother Chucked, if you mention any of these characters on the forum, the creator, Tim Buckley, will ban you for life.
 * R.H.Jr's 'Goblin Hollow' had the hell retconned out of it. It was once known as 'Under the Lemon Tree' and the Goblins were originally figments of Ben's imagination made real. It received a retcon changing the setting, and quite a few facts from the original, including how the goblins came to be.
 * Parodied in an oddly confusing fashion by Evil, Inc.. See the strip here.
 * Nikki in The KAMics was told by the author that she was a fictional character without a name, was later named by a reader, then it was retconned that she was a sister to the ex-Valkyries Gertrude & Brunhilda & her name had always been Nikki & she didn't realize this because of amnesia.
 * Gunnerkrigg Court, maybe. In the first chapter, Anne reconstructs a robot from spare parts in order to carry a shadow across a bridge (it was the only logical answer). To many, this implied that she was at least somewhat technologically proficient, as she is able to look at a piece of what we assume to be complex machinery and repair it almost completely. However, as the comic continues, we learn that her best friend Kat is actually the scientist and Anne is perplexed by machinery if anything. So, how did she rebuild a complicated gizmo like Robot? Well, we learn that all she really did was snap his fully functioning joints together (showing she is at least familiar with the "Head bone's connected to the neck bone" song), and didn't actually need to mess with his hardware to reboot him. Of course, after it was repeatedly shown that this golem-core adapts to completely new body type in seconds, it would be more surprising if anything in the Court robots' "proper" bodies required more setup than plugging cables in right type of sockets until everything is linked to the center and power source.
 * Erfworld recently needed to retcon a special ability given to one of the characters in its series. Funnily enough, it actually managed to successfully lampshade this through the ironically-recursive introduction of a school of magic known as retconjuration. (In an even more delicious twist of irony, this school retroactively replaced a school called Deletionism, which was, well... deleted.)
 * Drowtales went through this once. Now the first episode has been redone the second time. While the new pages are much better quality-wise, and some of the plot make a lot more sense, many elements were removed, characters have been changed, and episodes were cut down to mere sketches of their former selves. Not to mention the mysteries the reader was left in the dark about for most of the original stories were also revealed retroactively, taking away the suspense that provided most of the enjoyment. The series also became Lighter and Softer, and considering the world setting, that's not necessarily a good thing.
 * Lampshaded in this Darths and Droids
 * Comic book theme web comic Ret-Conned is named after this.
 * In The B Movie Comic, Professor Dr. was never actually a hunchback.
 * Bob and George: Why make it a plan!
 * Super Effective has done it a few times quietly--literally editing the comic and uploading a newer version. Changes include renaming Gary to Blue, for example.
 * Girly does this rather jarringly during the final arc. Turns out that  is actually the Eldritch Abomination-y Sidekick Queen, and that her entire life was just a lie fabricated to awaken her latent power. Entire strips were replaced to support this.   and the readers were devastated.

Web Original

 * Not altogether uncommon in Survival of the Fittest for example, from the V3 Pregame to the start of the game itself, Sean O'Cann went from a narcissistic, arrogant Jerk Jock with hints of homosexuality to a friendly, compassionate, fairly sensitive guy. This change seems to rely on the assumption that a couple of pregame topics (which featured Sean acting like a Jerkass) never happened.
 * Also, Bobby Jacks' full name. It transpires on the 7th day of the game that his name is actually Robert, with Bobby being a nickname. No reference of this being the case had been made before this point, although some people assumed that his name was Robert prior to that, but it's never mentioned, and his profile doesn't even note it.
 * Finally, the setting itself was Retconned, changed from being set in the Battle Royale universe to its own original continuity and setting.
 * LG15: the resistance applied a couple of these to Lonelygirl15, such as the revelation that Sarah or that Jonas.
 * Lampshaded in Unforgotten Realms where in one episode, Garry got his original body back (in a way that doesn't make sense), and jumps off a cliff. Two episodes later, Roamin talks about how the show does not make sence, and Garry reappears in his new body.
 * In the Homestar Runner toon "email thunder", it turns out that  This is expanded upon in "Hremail 7", where it's revealed that
 * Orion's Arm has made a number of retcons since it's creation. Femto-tech was removed due to physics problems. The number of people killed by GAIA was retconned a number of times in order to adjust the population numbers.
 * While not happening all the time, it is not uncommon for certain characters to be retconned in Marvels RPG. This will mainly happen if a new member wish to use a scrapped character that haven't done much before (s)he was scrapped.
 * The My Little Pony Friendship Is Magic fanfic "Pattycakes" was first written so that a badly derailed Fluttershy broke Rainbow Dash's will and caused her to regress to a childlike mental state. Given that a) the psychological torture involved consisted of bondage mitts, oatmeal, a bottle and a nappy and b) the whole thing took less than a day, a second part still referred to Dash as "mentally broken" but hung part of the plot on Dash's condition being the result of a mental regression drug Fluttershy had invented.
 * Whateley Universe: Word of God says that the author of the Phase novels only started years after the series started, and reinterpreted everything she didn't like about Phase's behavior in such a way that there were no outward changes (everything in prior stories was 'right' or 'slightly misheard') but all of Phase's actions were explained.

Western Animation

 * Futurama, "The Why Of Fry". This fourth-season episode posits that the original accident causing Fry to be frozen and sent forward into the year 3000 was actually intentionally caused by Nibbler and the Nibblonians so that he could save the universe from the giant space brains. At first glance, this seems like a retcon; however, careful viewing of the original first episode shows the shadow of Nibbler underneath the desk as the accident happens and in a revisited scene his eye stalk poking out, proving that the producers of the show set this up from the very beginning.
 * Perhaps the most jarring retcon of the movie was the fate of Fry's dog in the 2000s.
 * And speaking of Manly Tears,  Completely worth it for that song.
 * Speaking of Bender, Bender caused the alien apocalypse we see in the first episode.
 * Kim Possible: While it was never mentioned in the show proper, the Word of God in the beginning was that Shego's plasma hands were due to some technology in her gloves. She was eventually turned superhuman, shown using her abilities barehanded, and even given a Super-Hero Origin Backstory. Note that the official website still has the original explanation.
 * In one first season episode the original explanation seems to be shown when Shego doesn't have her gloves on, but doesn't bother to attack Kim when she could.
 * The Justice League cartoons get rid of most of the annoying retcons in The DCU, but they make a few new ones. Doomsday showed up in the original Justice League episode "A Better World," in which he said he was an alien invader looking to see what Earth had to offer in the way of worthy opponents. He's never heard of Superman before and doesn't seem to care one way or another about him. Later on in Justice League Unlimited he was retconned to be a creation of Project Cadmus, who reverse-engineered him from Superman's DNA and conditioned him to hate Superman above all else. Then, to explain his appearance in the older episode, Cadmus shot him into space for no good reason. He even got a completely different voice.
 * It happened again in the Fully-Absorbed Finale for Batman Beyond, which threw together plot points from dozens of episodes and two movies into something they clearly weren't originally meant to be. It's cleverly pulled off, though, as any potentially created inconsistencies are rather smoothly handwaved by a line from the creators, stating that their choice to have  was partly motivated by them realizing how.
 * In The Simpsons, the series has gone through a retcon as of the episode "That 90's Show." In the earlier episodes, Homer and Marge attended high school in the late 1970's got married three or four years after graduating from high school after Marge became pregnant with Bart, Bart was born in 1980, Lisa was born in 1983, and Maggie was born in 1990, but the series was retconned in the aforementioned episode. Marge in previous episodes had never gone to college, but was suddenly attending in the mid 90's; it led us to believe Homer had a Grunge band, whereas in an earlier episode he didn't understand grunge at all; and they also showed us that they dated for at least ten years before getting married and having the kids, who are now retconned into being born in the early 2000's.
 * Prior to this the characters were stuck in the 90's and never aged.
 * The Simpsons time line being what it is, this retcon actually makes sense. The Simpsons' time exists on a sliding line, so even though every episode happens in "the present", the past keeps moving forward. Also note that while the kids' age never change, Marge and Homer have been, albeit very slowly, getting older; being in their mid-thirties in early episodes and now nearing forty (presumably to reflect the aging American population), which does leave a gap for the events of "that 90's show" to take place.
 * The writers have made clear that some things are immune to the sliding time gimmick. Grandpa Simpson and Mr. Burns will always be WW 2 veterans, even if that makes them unrealistically old. They will also have both known the Great Depression.
 * Also on the subject of Mr. Burns, he started out at 81 years old (the early episode where Homer defrauds the plant's health insurance for hair growth), but is now canonically 104 years old.
 * As at this writing, Simpsons is now in its 22nd season. That's not Retcon, it's maths.
 * Mr. Burns had been mentioned to be 104 as early as season 6. Although, his age is basically debated, many of his other mentioned possible ages place him as being older than 104, some place him at 118, others at 122.
 * Unrelated to the sliding timeline, one glaring aspect that was essentially retconned from the show is Homer's relationship wtih his mother. In the fourth episode, "There's No Disgrace Like Home", Homer mentions that his mother said he was a big disappointment. However, if "Mother Simpson", "My Mother the Carjacker", and "Mona Leaves-a" are any indications, Mona Simpson has always loved Homer and it's doubtful she would've ever said anything of the sort.
 * Likely a case of Characterization Marches On, given that it occurred so early on in the show's run (same episode has Homer pawning the TV set so that his family can learn some manners), and very little was made of their relationship in between. Arguably, it was a retcon for "Mother Simpson" to establish that Mona had been alive all this time, when it had been implied up until then that she'd died, but then the details on Homer's mother had always been very vague.
 * As for the whole 90's ret-con, it helps to clear up one glaring Plot Hole that Jon Stewart once pointed out to Matt Groening in an interview. Homer and Marge were supposed to be in their late 30s. They got married when they found out Marge was pregnant with Bart, but since Bart is only 10, about a decade would had to have passed between high school and Bart being conceived. Lisa even lampshaded said plot hole in the episode.
 * Even that was a retcon. In the early seasons Marge and Homer were 34 and in Season Two (1990) it was revealed they graduated in 1974, giving them a birthdate of 1956. Bart was born in 1980, six years after they started dating. The retcons started happening fairly fast though. By Season Four Lisa was given a birthdate of 1983 and Bart was said to be two, giving him a birthdate of 1981 but in the same season Marge and Homer were still part of the 1974 class.
 * King of the Hill: In, when Cotton tracks down Hank and company in the Japanese restaraunt, it triggers flashbacks in him, and he calls the Chef (who only speaks Spanish) a Tojo, his slur for them. However, wasn't part II of Returning Japanese basically about him , talked out of his scheme to spit in the Emperor of Japan's face by ?
 * For that matter, that episode Flanderizes him back into the Jerkass, verbally Abusive Parent he was at the beginning of the series, throwing out his Character Development into a Jerk with a Heart of Gold.
 * The series has had some arguably even more annoying retcons.
 * Peggy's background was rewritten so that she spent most of her early life in Montana, rather than spending her high school years in Arlen. This complicates the episodes where Hank and Peggy are shown as High School Sweethearts. Meanwhile, Peggy's mother changed from an older-looking version of Peggy who was just hyper-critical into a totally different looking woman who was a downright bitch.
 * Luanne's father/Peggy's brother didn't appear until near the end of the series, though was mentioned several times. Originally, he had fled to an oil rig in fear of his abusive ex-wife, refusing to come back on land until Hank faxed him her death certificate. Bill mentions him looking like a male version of Peggy while Hank mentions getting along with him. When he shows up, however, he is revealed to have actually been in jail for years for being a con artist and thief, a fact which Peggy hid from everyone with the oil rig story. He also looks nothing like Peggy and it seems that Hank had never met him before.
 * This change calls forth several bits of Fridge Logic: one, Luanne is supposed to have seen the event that caused him to flee to the oil rig; how does his incarceration fit into that event, especially since we know her mom was put in jail herself for that abuse? And if she was already in jail, why did Peggy (and later Hank) think it would be so traumatizing for Luanne to also know that her father was as well?
 * Also they established several times that Luanne witnessed the fight between her parents that led to her mom stabbing her dad with the fork which occured in the very first episode where she was about 16 or 17, but in this episode her dad claims the last time he seen her she was a little girl about five years old and she has no memory of the event.
 * Hank and his old Arlen High School football team challenged the team that they lost against during the championships to a rematch that they eventually win. This one is made more annoying by the fact that Hank had come to terms with losing the game in an earlier episode. It left a bad taste considering it was one of the last episodes.
 * Another would be the origin of Dale's Rusty Shackleford identity, in a couple of early episodes he mentions he got the name from a boy who died from smallpox back in the 1950's, however it was later retconned in the season 11 episode "Peggy's Gone To Pots" where he supposedly got it from a boy who went to his school and moved away and Dale thought he died, and the "real" Rusty Shackleford arrives to tell him to stop using his name.
 * Thomas the Tank Engine: Reverend Awdry stated that the North Western Railway was built in 1914, mainly by Edward. In the 2009 movie Hero of The Rails, it is stated that the new character Hiro was responsible for building it. This may sound like a standard Ret Con, but keep in mind that Hiro is a JNR class D51, which wasn't built until 1936. And it doesn't help that Hiro is Japanese and thus runs on a completely different gauge than traditional British engines...
 * Dexter's Laboratory - in the fifth episode we are introduced to Dexter's rival, Mandark, who had just moved into the neighborhood as an exchange student. He introduces himself as Astrononminov (Possibly his last name, but prefers to be called Mandark. He was a fairly competent villain, at least when Dee Dee wasn't around, and he had a sister named Olga Astrononminov that prefers to be called "Lalavava". In the last two seasons, which were made a few years after the series had ended, Mandark is now named Susan and has a pair of hippie parents and He and Dexter supposedly first met when they were little and became a villain because Dexter made fun of his name. He's nowhere near as decent of an antagonist as he was in the early episodes.
 * In the original Fairly Oddparents pilot, Vicky was apparently babysitting Timmy for the first time, and Timmy was ten. The first movie reconned both points: Vicky had been Timmy's babysitter for a year, and Timmy was nine when he first got Cosmo and Wanda.
 * In the Jonny Quest made for TV movie Jonny's Golden Quest, Jessie was revealed to be the daughter of Race Bannon and his mysterious lover Jezebel Jade, during a brief affair the two had. In the second season of the next series The Real Adventures of Jonny Quest, the new writing staff created the character of archeologist Estelle Vasquez to be Jessie's mom (and Race's ex-wife) since they believed Jade wasn't the kind of woman who would settle down.
 * Jesse Bannon herself was a retconned version of Jesse Bradshaw, a character who appeared in an episode from the 80's series The New Adventures of Jonny Quest. The original Jesse was not related to Race Bannon.
 * In the Ben 10 Alien Force, episode "Be-Knighted" the evil group the Forever Knights revealed that their ultimate goal was to slay an alien dragon they had captured (later a whole planet of them) as opposed to conquering the world, as they had attempted in the original series (they even had a different leader than was seen in the older series as well). Series writer/producer Dwayne McDuffie later revealed this was, in fact, their goal from the beginning and the Forever Knights Ben fought in the original series (led by former Plumber Driscoll as the "Forever King"), was actually a rogue splinter faction of the original group and that the king Patrick, seen in "Be-Knighted", was the true Forever King and Driscoll was an imposter, or something.
 * There's also changing the nature of Gwen's magic due to being part alien and turning the Plumbers from a defunct federal Men In Black-esque agency into a still-active intergalactic police force.
 * The Season 14 South Park episode "201" retcons the twist ending of "Cartman's Mom Is Still a Dirty Slut", from way back at the beginning of Season 2 (twelve seasons before) by revealing that Liane was Cartman's mother all along and her claim of being a hermaphrodite was simply a cover-up to protect the identity of Cartman's real father, the former right tackle of the Denver Bronco. Said Denver Bronco turns out to be none other than Jack Tenorman, the man Cartman murdered and fed to his son Scott in the Season 5 episode "Scott Tenorman Must Die". Cartman seems more upset at the fact that he is Scott Tenorman's half-brother, thus making him half-ginger, than with the revelation that he killed his own father and then fed his remains to Scott.
 * He feels better when Mitch Connor reminds him of the fact that he's also half-Denver Bronco.
 * South Park also gives us what is possibly the most epic retcon ever. In the second episode of the "Coon and Friends" trilogy, Kenny reveals that he can't die. He explains to another superhero that he's died many times in the past, and just ends up waking up in his bed like nothing happeed, with only he remembering his gruesome demise.
 * In the most recent episode Tuong Lu Kim the Chinese resturant owner is revealed to be another personality of Dr. Janus a doctor who suffers from multiple personality disorder, for all we knew in his past appearances he was an authentic Chinese man.
 * In "Mr. Hankey The Christmas Poo", it's established that Kyle's family were the only Jews in South Park. Later in "The Passion Of The Jew", we see that there are more Jews as well as a synagogue (though the synagogue first appeared in "Cartmanland").
 * One of the more blatant revisions of past events in a series came in the form of a bit of dialogue found in the 9th season Family Guy episode "Excellence in Broadcasting". In said episode,when the Griffin family hears that Rush Limbaugh is coming to town to promote his latest book,Chris recalls that in the episode "Fox-y Lady", during Lois' brief stint at Fox News, she reported that Limbaugh as well as Michael Moore were characters played by Fred Savage, something Lois dismisses by explaining that, even if something is true, once it is said on Fox News it becomes a lie.
 * The episode "Brian: Portrait of a Dog" shows Peter adopted Brian as a stray when he was washing people's cars to earn money, however in "The Man With Two Brians" shows the Griffins got him as a puppy.
 * In the fourth episode of American Dad it is said that Roger has been living with the Smiths for four years after Stan rescued him from the C.I.A.,however in a much later episode Stan in a flashback gives him to Steve as a little boy for his birthday.
 * Plus: this episode was basically just a parody of "A Boy and his Alien" stories, and both Steve and Roger seemed to be kind of in on the joke. So the flashback was probably just for fun, not as a legitimate backstory.
 * Lampshaded in Frisky Dingo. In one episode, Grace Ryan is seen taking "Ret-Con" brand ant poison to cure herself of her Super-Powered Evil Side Antagone. In another episode, it's explained that the Annihilatrix has been completely rebuilt, despite previously having been stripped down for scrap. A quick cut shows that the rebuilding was done by "Ret-Con" Construction Company.

Real Life

 * Stalin was constantly re-writing the early history of the Communist revolution and the USSR to remove opponents from history or take credit for their accomplishments, even when the resulting version made no sense. A few of his successors continued the practice. Stephen Jay Gould once reported reading a version of the Soviet Encyclopaedia that completely removed Stalin from history, which is kind of like trying to tell the Star Wars original trilogy as "The Jabba The Hutt Show!"
 * There are examples of crude (by our standards) photo shopping. One can find photos where Trotsky and others he'd killed have been removed, and other photos where he is shown next to Lenin as the latter fell sick and died (even though at this time Lenin had started to dislike Stalin).
 * Similarly, during the space race many Soviet cosmonauts that had perished on failed missions were supposedly edited out of group pictures taken with their equipment.
 * The 2006 reclassification of Pluto as a dwarf planet.
 * It was starting to get embarrassing as more and more trans-Neptunian objects were discovered that were of a similar size (one of them, Eris, is larger). The main argument for keeping Pluto a planet was seemingly for "cultural" (read: sentimental) reasons, so the "dwarf planet" term was applied by means of a compromise: still significant in its discovery and in terms of its mass compared to the other discovered Kuiper belt objects, but emphatically not a regular planet by the IAU's definition. Eris, Haumea, Makemake and Pluto itself were additionally classified as plutoids to honour Pluto's historical significance.
 * If one were so inclined, they could argue that a dwarf planet is a category of planet. We've got gas giants, after all, though this isn't nearly as precise a term as dwarf planet. Ultimately, though, it's a matter of scientific terms, much like the disparity between the scientific usage of theory and the common usage.
 * The argument over the classification of Pluto mirrors that of Ceres, which was considered a planet when it was first discovered in 1801 but downgraded soon afterwards when other asteroids were found. It was reclassified as a dwarf planet at the same time as Pluto.
 * In 1660, the restored Royalist regime in England declared that the eleven years of republican rule had been "invalid" since no monarch had been there to give assent to the various laws parliament had enacted. A legal fiction was created where Charles II's reign was backdated to 1649 and the 1649-1660 Cromwellian era was described not as a republic but as an "interregnum" (ie a period where a kingdom had no king). Despite very few modern historians playing along with this, the term "interregnum" is still frequently used to describe the Commonwealth period even though the monarchy had been abolished.
 * Charles was proclaimed king by the Scottish parliament only a few days after his father's execution, and was even crowned at Scone before he had to flee to the Continent, so technically, his reign could be described as beginning in 1649.
 * Which would only make him King of Scotland, meaning the throne of England was still vacant.
 * Similary, the Bourbon Restoration decided to ignore both the First French Republic and Napoleon's rule. They declared the son of Louis XVI (who was executed in the Revolution) to be King Louis XVII, though he never ruled, and Louis XVIII counted his own reign from 1795, when Louis XVII died, instead of 1814, when he actually came to power.
 * And when Bonaparte's nephew Louis-Napoleon took over in 1852, the Restauration was considered as 'Second Empire'which is why the Third Empire follow's Bonaparte's First.
 * In the early hours of April 1, 1964, the Brazilian military took over in a coup d'etát and ushered a 20 year long dictatorship. Predictably, they retconned the coup date to the day before.
 * Henry VII officially dated his reign from the day before the Battle of Bosworth, i.e., the day before he finally became the Last Man Standing in a decades-long game of Kingmaker.
 * This was a very smart move. He could then take land away from any lords who fought against him in the battle, as they were traitors opposing the king.
 * Common practice in North Korea, especially about details regarding Kim Il Sung, Kim Jong Il, and The Korean War. One story of Kim Jong Il's birth was that North Korean soldiers stationed in the mountains near his claimed birth-site had a premonition that something wonderful was happening at the time he was born. To mark the occasion, they carved the date into a tree. This tree was then shown to visiting foreigners... until a Japanese botanist pointed out there's no way anyone could have carved something in that tree on that date because the tree was not that old and would not have existed. The tree was silently cut down and never referred to again.
 * Some automobile magazines do not consider the Volkswagen Logus to be in continuity with the Ford Escort line, despite being related to it. Why say it's not related, when it uses an adaptation of the Ford Escort chassis?
 * After World War II, the Vichy Regime was retconned by French President François Miterrand (a member of the Resistance) into being nothing more than a fake government, while Charles de Gaulle was the true head of state all along. This does not prevent a lot of historians from wondering wether France was in Vichy or in London at the time.
 * Pope Gregory XIII decreed that the day after Thursday, 4 October 1582 would be not Friday, 5 October, but Friday, 15 October 1582, this was due to a miscalculation of days in the Julian calendar that had caused the Vernal Equinox to seemingly change from the traditional March 21 to March 11. Since the Church scheduled Easter based on the first day of Spring, the retcon was seen as necessary.
 * Nobody remembers the Armenian Genocide, but the Turkish government will assure you that Turkey never did anything evil in Armenia.
 * Birthers retcon the teaching of U.S. naturalization law and civics, contending that they were always taught since childhood that a natural born citizen is someone born to two U.S. citizen parents. So far, nobody has been able to provide any sort of Civics or Law textbook published before 2008 that mentions this.