Butterfly of Doom

""Don't do anything, don't touch anything, Sci-fi rule number 1: you start messing with the past, you end up with monkeys ruling the future.""

- Cyborg, Teen Titans

Want to go back in time to stop your parents from losing their retirement money in the Dotcom crash? Save a loved one from a fatal accident? Nudge a closet a little to the left to avoid hitting your toe? In some universes, you're not just going to run into You Can't Fight Fate, but into Finagle's Law on a grand scale: the Butterfly of Doom. Any and every change made in the past will always have an unintended and horrible side effect. Much like a temporal Monkey's Paw, the initial effect might come to pass, but at a terrible cost. Telling your parents to move their money elsewhere gets you arrested for inciting a financial panic and insider trading, the loved one you saved develops a wasting terminal cancer, the closet you moved is now on a weak floorboard and crashes through it, and because of termite damage collapses the rest of the house killing you in the process.

Generally part of a story about accepting things as they are, this is the sword held over the heads of repeat offenders of Hitler's Time Travel Exemption Act, those who insist on changing the past. The resultant world can range from a dark Alternate Universe to a full-blown Mirror Universe. Heroes can usually Set Right What Once Went Wrong, by undoing the original change with a bit of Rubber Band History. Curiously, these changes are never positive, suggesting in all cases shit happens for a reason.

Intuition dictates that big changes have big causes, and small causes equal small changes. This trope is named partly for the Butterfly Effect, an observation made in meteorology. In the large-scale computer simulation of weather systems, a minuscule change in temperature or the wind's direction (about the bat of a butterfly's wings) will drastically alter the weather (sunshine instead of hurricanes) simulated at a later point. Even if the models used work, it is impossible to achieve sufficient accuracy when entering the data. Thus computer-assisted long term weather forecasting is considered a joke even by meteorologists.

The Of Doom is appended because the image of a single frail, pretty, delicate-as-a-sheet-of-glass butterfly causing the world to turn itself inside out is amusing. In Real Life, the butterfly does not actually change the expected mix of storms; a flap of the wing may cause hurricanes, hailstorms, typhoons, tornados, blizzards, but it would be equally likely to prevent those storms. Probably it causes about an equal number of both changes, but the Butterfly Effect makes it impossible to tell which ones. That being no fun at all, writers tend to opt for the Doom scenario.

This alone may be a bad reason to argue for a universal butterfly effect. Edward Lorenz's Chaos Theory is based on the idea that an unstable system is unpredictable and a small change can have a large impact in the long term. Not all systems are unstable, though. This is why there is no scientific reason to claim that the whole universal system is unstable as well. Further, "Chaotic" does not mean entirely random. Systems defined as "Chaotic" may be unpredictable, but they still are deterministic. That is to say that if you knew the exact value of every parameter that influences the state (the weather) at a given moment, you would be able to predict the state of the next moment (forecast the weather). Precise knowledge of every parameter, however, is a difficult assumption to fufill and is physically impossible with current technology and knowledge in the context of weather in nature due to Heisenberg's Uncertainty Principle.

The butterfly effect also refers to Ray Bradbury's seminal time travel story "A Sound of Thunder", which centered on the disastrous consequences of a butterfly's death. By marvelous coincidence, the story was written ten years before Lorenz began pondering the inaccuracies of his forecasting computer.

In theoretical discussions of Time Travel, this phenomenon is sometimes referred to as "Avalanche Time", evoking an image of cascading changes that race forward through the timeline exponentially, obliterating everything familiar to the time traveler who set it off.

There is a philosophical history regarding this trope as well. Leibniz theorized that God made this the best of all possible realities. Ergo, any change would be tampering with perfection. Therefore in Western Media the Butterfly Of Doom is God being sort of a dick. (Leibniz's philosophy was parodied in Voltaire's Candide, with Doctor Pangloss who, no matter what horrendous atrocity he beheld, would exclaim that every thing was for the best in the best of all possible worlds).

The most common aversion of this trope is based on the idea that large scale historical processes happen for large scale reasons. The Butterfly of Doom may alter the course of a hurricane, it can't stop winter from changing into spring.

See also the Aesop of Wonderful Life. See also Finagle's Law, Hitler's Time Travel Exemption Act, You Can't Fight Fate. A subtrope of For Want of a Nail. Merged Reality is the opposite scenario. Godwin's Law of Time Travel is a subtrope of this.

Has been known to team up with Schrodinger's Butterfly to cause mind breaking havoc. See also Save This Person Save the World for when the Butterfly of Doom is a person.

Compare Rube Goldberg Device.

Anime & Manga

 * Almost the entire point of all events in XxxHolic. Interesting that Yuuko's symbol is the butterfly, though that falls under another butterfly trope.
 * In an episode of Penguin Musume, Kujira learns that she confessed her love to Sakura when they were both young girls (Kujira was raised as a boy.) Embarrassed into action, Kujira takes the Time-Penguin-X1 (yeah, you heard me) back to prevent herself from confessing. After older-Kujira realizes she's made a horrid mess, she works to repair the timeline, causing her younger self to instead make a marriage vow. Hilarity Ensues.
 * Basically the entire plot of The Girl Who Leapt Through Time. Though Makoto never tries to change anything particularly big (she uses it for stuff like repeating a karaoke session over and over for several hours), once or twice she changes something small that has massive and unexpected repercussions. After several failed attempts at matching a friend with a girl who who likes him by leaping back in time, she finally gets it right.

Comics
"Xavin: As usual, you're missing the bigger issue. What you should be worried about is the Butterfly Effect.
 * In All-Star Squadron, the robot Mekanique is sent back from the future by the evil scientist Rotwang to prevent a car accident that will kill a small girl and a naval officer. Somehow, this change will prevent the rise of the rebel leader Maria in Rotwang's future who leads a slave rebellion that threatens to overthrow the ruling elite.
 * Mentioned, though not actually applicable in the Runaways time-travel arc:

Chase: Dude, I'm totally on top of the Butterfly Effect! (aside, to Molly) What were they, like, bigger?"


 * Fifty Two has a  example.  Okay, so maybe
 * Pinky and The Brain (Yes, this is a comic story instead of a cartoon) once went back in time a few hours to prevent their past selves from opening a savings account at a bank that would be robbed afterwards. (They had a time machine that Brain planned to use to go to the future to get the money plus interest) When they returned to their own time, they found the world being ruled by ostriches. (No, really)

Films -- Live Action

 * The majority of the first Back to The Future movie is Marty trying to reverse the effect of his having saved his father from being hit by a car.
 * Over the course of the trilogy, changing the past has nothing but positive effects for most of the characters. But not intentionally. In fact, almost all of Marty's intended timeline changes end up nearly erasing him from existence. All the positive changes came from unintentional changes -- most notably his "Darth Vader from the planet Vulcan" schtick, intended to spook his teenage dad into asking for a date, instead gave him confidence to become a professional science-fiction author.
 * Part 2 has an ideal example with the Timeline-Altering MacGuffin. Marty buys it to make a fortune in sports betting. Doc finds out and throws the almanac away, Biff from 2015 finds it. Old Biff then steals the time machine and gives it to himself in 1955. This then causes Biff to become the richest and most powerful man in the country, single-handedly legalizing gambling, ensuring Nixon's re-election for multiple terms, and turning Hill Valley into a Crapsack World where biker gangs rule the streets and armed thugs ride around on tanks.
 * You forgot to mention he married Marty's mom and killed Marty's dad!
 * In a deleted scene, where Old Biff brings the DeLorean back to 2015, he fades out himself. Presumably, Lorraine finally got up the courage to off him sometime after 1985a. So the "stuff you do on purpose turns out badly for you" rule still holds.
 * you could also say that this movie averts this trope. While some of the things he does ends up with a bad outcome, other smaller things that should create a terrible effect by the trope's standards end up making life better for them in the future, meaning the old future wasn't necessarily the "right one."
 * "Timewaves" are the result of the change in history in the very loose film adaptation of A Sound of Thunder.
 * And let's not forget the movie The Butterfly Effect, named for the effect that names this trope.
 * The Butterfly Effect is also notable for  Only in the director's cut, not the original theatrical release ending.
 * This is played with in Donnie Darko; the setup is the same, and the plague of strange events that follow lead him to return in time.
 * More than that,
 * Inverted in 2002's movie adaptation of The Time Machine, wherein Alexander Hartdegen's repeated attempts to go back in time to save his fiancée Emma inevitably go wrong. Later, the Uber-Morlock explains that the reason he cannot save Emma is that her death was his prime motivation for building the time machine.
 * In the film Frequency, a shortwave radio and the Northern Lights allow the main character to communicate with his father thirty years back in time.
 * Dennis Quaid's character actually lampshades this trope during the film.
 * The movie Sliding Doors had a non-time travel variation. The movie follows the events following the protagonist either missing the subway or getting on just in time, and then some...
 * The film Mr. Destiny starring Jim Belushi as Larry Burrows, an unhappy middle aged office employed loser. He blames the state of his life on the moment he struck out in a high school baseball game. A guardian angel like figure named Mike (played by Michael Caine) changes the past so that he hit the ball. Larry is now the president of the sporting goods company he worked and married to the owner's daughter. However, he soon learns that his alternate self's other decisions have a number of problems: his father is now divorced (on "his" advice, no less), he's having an affair with an Ax Crazy worker, his best friend is now afraid of him, he's been involved in some shady schemes with the other executives who are now plotting to get rid of him after noting his "change of heart" and his wife from the original timeline is now married to someone else.
 * In the Stargate Verse film Stargate: Continuum,  has gone back in time and killed one man, . This is made more interesting when the main characters, who know about the normal timeline, ask to be allowed to fix things, only to be told by General Landry that the people in this timeline don't want to be involved in big intergalactic wars. They like things just fine the way they are.
 * He also points out that by restoring the timeline, the lives of everyone in the altered timeline are changed, and many will cease to exist -- like Jack's son, Charlie, who is alive in the alternate timeline.
 * Perhaps the Aesop of Lola Rennt is that it's all just a crapshoot. Any given ripple of influence from a chance passing could be a Butterfly of Doom -- or a miraculous windfall -- for Lola or anyone she brushes with. The opener alone establishes that fighting fate is just a game.
 * Fish Story is one big butterfly effect, tracing from the initial recording of a before-its-time and rapidly forgotten musical number to how that particular bit of music sets in motion a chain of events that saves the world.
 * Invoked in the Terminator franchise -- in that it is the machines' plan to alter their present by meddling with the past. And yet curiously averted in that they kill a whole bunch of people other than Sarah or John seemingly without affecting anything.
 * Technically those people were dead anyway. Judgement Day pretty much cleared the decks.

Literature

 * The archetypal example -- from which the trope name descends -- would be Ray Bradbury's 1952 short story A Sound of Thunder.
 * Similarly, the science-fiction story "Aristotle and the Gun" by L Sprague De Camp has an arrogant time traveler trying to change history, and achieving the exact opposite of what he intends.
 * Both the novel and the film Millennium conclude with a runway "timequake" obliterating the future, because of an accidental change made to the timeline in the present.
 * An Animorphs Super Special dealt with a villain changing time. Some things were better, some things were worse; World War II, of course, was one of the affected areas. Much of the conflict of the book is over whether to restore the world or keep it the new way, and what justifies preserving bad pieces of history.
 * There was also another storyline where we find out what would have happened if the main characters hadn't run into the alien who gave them superpowers and warned them about an alien invasion.
 * In fact, Cassie's history teacher Ms. Paloma makes a reference to the butterfly thing in Book 7, The Stranger. See here.
 * The Green Futures Of Tycho by William Sleator involves a time traveler teenager making repeated trips into the future. Each time he discovers a bad future, and tries to fix it in the present or past. Each time, his actions only make it worse. He eventually realizes the reason, but not before he gets his time-traveling Evil Overlord future self chasing him to stop himself from messing up the past (present for the teenager) that lead to his present (future).
 * Isaac Asimov's novel The End of Eternity. Only in this case, the constant changing of the potential timelines by a secret trans-temporal time agency resulted not in unpredictable chaos but in a static history, because the time agency tried to erase, with the best intentions, every invention, trend or development that they regarded a danger to Mankind and human life in general... erasing wars, but also deliberately killing all attempts at space exploration throughout the various millennia. In the end, only the destruction of the time agency itself allowed the restoration of Mankind's original timeline: a life full of risks in search of the Unknown, but also with the potential to colonize the galaxy and survive into the distant future after the Earth's sun had gone nova.
 * This was subverted in Terry Pratchett's The Last Continent. When the faculty of the Unseen University find themselves trapped centuries or even millennia before they were born, Ponder Stibbons invokes the ever-popular "kill your own grandfather" example of why you shouldn't muck around with the past. Arch-chancellor Ridcully dismisses Ponder's concerns with a logical "whatever happens stays happened" attitude. He points out that having killed one's own grandfather and ceased to exist, no-one would exist to step on the ant, meaning your grandfather was never killed. This creates a circular paradox; doing something makes you unable to do it. He also observes that he is unlikely to kill his own grandfather, as he "rather liked the chap." Therefore, since they are in the past, they were clearly there once already (i.e. now), and therefore any ants that are stepped on, are vitally important in their capacity for being stepped on. The Bursar later attempts to take this to heart by jumping around on ants in between walking into trees.
 * This subversion of the Butterfly of Doom theory is itself a well-respected alternate theory of how time travel might work; in a real sense Ridcully is simply the Discworld inventor of an idea that many writers of time travel stories already accept in our world.
 * Directly parodied with the Quantum Weather Butterfly, flocks of which played a big part in Interesting Times. The Quantum Weather Butterfly uses its ability to affect localized weather phenomenon as a form of self-defense, and possibly a way of attracting mates. "Hey baby, look at this thunderstorm!" (And of course, Pratchett Shows His Work by pointing out that the fractal nature of the edge of the Quantum Weather Butterfly's wing makes it quite finite in area, but nearly infinite in perimeter, which is one of the seeming paradoxes of fractal surfaces in real life.)
 * Alas, no. While probably a deliberate 'error' attributed to Discworld logicians, the statement in the book is actually less mathematically sound:

"And therefore, if their edges are infinitely long, the wings must logically be infinitely big."

"They may look about the right size for a butterfly's wings, but that's only because human beings have always preferred common sense to logic."

"Lu-Tze: We're learning a lot, though! For a perfectly logical chain of reasons Vimes ended up back in time even looking rather like Keel! Eyepatch and scar! Is that Narrative Causality, or Historical Imperative, or Just Plain Weird? Are we back to the old theory of the self-correcting history? Is there no such thing as an accident, as the abbot says? I'd love to find out!"
 * Pterry plays with theories of time travel/the Butterfly Effect a lot. A good example is Night Watch, where despite the fact that when John Keel, an important figure in the storyline, is killed because Vimes turns up 30 years in the past, Vimes ends up taking his place more-or-less seamlessly. Lu-Tze, the history monk, muses on the nature of time:


 * and later...

"Vimes: I mean, doesn't it change history if you tread on an ant?

Qu: For the ant, certainly.

Lu-Tze: I told you, Mister Vimes. History finds a way. It's like a shipwreck. You're swimming to the shore. The waves will break whatever you do. Is it not written, "The big sea does not care which way the little fishes swim"?"


 * Pretty much the plot of Madeleine L'Engle's A Swiftly Tilting Planet: Mad Dog Branzillo will succeed in nuking the earth unless
 * In the third book of The Pendragon Adventure, The Never War, the characters at first think that to make the turning point go correctly, they must stop the destruction of the Hindenburg. However, they ask the Traveler from Third Earth (the far future) to analyze what would happen if they did it. It turns out that the world would be destroyed if they went through with it. After a rather huge misunderstanding because one character didn't get that last bit of info, they manage to let time go on its proper course.
 * And then, in the later books, Mark brings incredibly advanced technology into the past, jump-starting the computer industry and advancing technology's development. Of course, also thanks to Mark, we also get the future dystopia seen in Raven Rise because of a stupid decision he made in 1939.
 * In Marge Piercy's Woman on the Edge of Time, it's implied that the apparently futile actions of a single patient in a mental institution will affect whether the future holds a sustainable, egalitarian utopia or a polluted colony of virtual prisoners and sex-slaves.
 * Alfred Bester's The Men Who Murdered Mohammed plays around with this. A scientist attempts to erase his wife's existence after he finds her cheating on him. He whips up a time machine, and goes back in time to kill her grandfather. The catch? It doesn't work. So, he works bigger, rampaging through time, killing more and more famous people with absolutely no effect on the present until, finally,
 * The Children of the Lamp series has a non time traveling example. Philipa (a djinni) grants an innocent wish of removing all foie gras from New York city. But it takes a horrible turn in that through an unusual series of events
 * A literal example of this shows up in a Phillip K. Dick story, where traveling to the future causes hordes of blue winged, acid secreting butterflies to show up and kill everything.
 * Invoked in a small way, along with Failure Is the Only Option, as part of a brutally satirical short story in Stanislaw Lem's Memoirs of a Space Traveller: The Further Reminiscies of Ijon Tichy. Attempts to correct problems in history and create a better world fail spectacularly due to a combination of mishap, incompetence, and malice; resulting in a thoroughly fouled-up world —- ie. the one we currently live in.
 * Hilariously lampshaded/satirized in William Tenn's short story "Brooklyn Project", which opens with the acting secretary to the executive assistant on press relations explaining to a group of journalists that the project to send a probe four billion years into Earth's past -- and then two billion, and then one billion and so forth -- is perfectly safe, that nothing that happens in the past can change the present. In brief vignettes we see the probe condensing moisture on its outer surface, the probe destroying microorganisms with its weight, the probe crushing tiny trilobites... and the story ends with "the thing that had been the acting secretary to the executive assistant on press relations" spreading his tentacles and explaining that as they can all see, nothing has changed.
 * Directly referenced in the fist chapter of the first Code Lyoko novel, "The Butterfly at the Bottom of the Sea". The butterfly is the miniscule disturbance of a cable deep beneath the Sea of Japan, and the end result is
 * Invoked in Scorpion Shards, where Dillon intentionally searches for the proverbial butterflies he can kill to cause huge catastrophes.
 * In The Wise Man's Fear the Cthaeh, an entity unable to leave a single tree, has perfect knowledge of all possible futures, and whenever it speaks to someone manipulates them into causing the greatest possible harm with just a few words. Policy on handling those who speak to it is to shoot them dead from half a mile away, leave the body to decompose, and if a crow descends to eat the body, shoot the crow.
 * The historians in Connie Willis's time-travel novels are afraid of this happening, because although for many years they've believe that the laws of time-travel physics don't allow anyone to travel if their presence will change history, this isn't borne out by their own experiences - while they can't visit "divergence points" (for example, the battle of Waterloo, or anywhere near Hitler) they can alter minor events, and then have no way of knowing whether this has had a significant effect. The plot of To Say Nothing of the Dog balances on whether two individuals will marry each other instead of the people that they're required to marry so that their descendants exist in the future in order to play historical roles, and in Blackout it's posited that a novice time-traveller bumping into a woman and making her drop her handbag may cause the Allies to lose WWII.
 * In the short story "You're Another" a hapless man finds that all of his troubles are caused by people from the future who alter the past, over and over again, and then film it as entertainment. When asked if changing the past doesn't change their time in the future they explain that it doesn't saying "What happens to a dog when you cut off it's mother's tail?" He is not happy when he finds out his part in all this, and why he's constantly falling into holes, having paint drop on him and being cheated on my his girlfriend. Their explanation.
 * Played With in 11/22/63. While changing the past does have majorly negative effects, this is the result of the timestream shattering.

Live Action TV
"Angela Petrelli: It's called the Butterfly Effect. You step on a butterfly today, three years from now a million people are wiped out."
 * Blackadder Back and Forth is a brilliant example of this trope. In the story, Blackadder (accidentally, initially meaning it as a scam to win a bet with his guests) invents a working time machine. He is sent on a dare to use it and to bring back a catalogue of different items including a centurion's helmet and the Duke of Wellington's boots. After he succeeds in doing these things, it emerges that he has changed the course of history as a result: After finally arriving at the battle of Waterloo, he squashes the Duke of Wellington with his time machine just before the battle begins, steals his famous boots and causes the French to win the fight. As a result, Blackadder returns to an alternate-reality Britain which has been ruled by the French for 200 years - as a result of his tampering - following Napoleon Bonaparte's victory at Waterloo, and just in time for garlic pudding. He becomes especially disconcerted when he sees Archdeacon Darling wearing a tutu and exclaims "We've got to save Britain!" before going back in time to try and rectify everything. He also has a run-in with William Shakespeare, earlier on in the story, whom he attacks for the interminable suffering of school pupils that would happen for the next 400 years as a result of having to study his plays at length, leaving William completely discouraged as a playwright but dropping his ballpoint pen in the process. Later on, in the alternate reality, William Shakespeare is revealed to have been known only for "inventing the ballpoint pen."
 * Subverted in an episode of Scrubs appropriately entitled "My Butterfly", where a butterfly affects the events of the day, ending in the death of a patient. When the butterfly changes where it lands, the episode features an alternate future, but.
 * Another fine example of how one man's repeated attempts at changing the past to find the "perfect" timeline are leading to ever more disastrous consequences is the two-parter episode "Year of Hell" from the 4th season of Star Trek Voyager. Things are spiraling out of control, precisely because the timeship is based on the idea of Laplace's Demon which is contradicted by both Quantum Mechanics and Chaos Theory. In the end Basically, a giant Reset Button finale, but one of the few times in the Voyager series in which the Reset Button actually made sense from the context of the episode.
 * In what is widely considered to be the best episode of Star Trek the Original Series (TOS), "The City on the Edge of Forever", the world falls to Nazi Germany and Starfleet never forms because one woman didn't die when she was supposed to.
 * The story -- originally written by Harlan Ellison -- had been radically revised, by the time the episode was shot. So much that Ellison asked to be cited under a pseudonym. It's unsure whether -- at least, in part -- his displeasure with the final result had anything to do with the story's subtext that opponents of the Vietnam War were comparable to appeasers of Hitler.
 * Played with in the Mystery Science Theater 3000 episode, Time Chasers, a nerdy scientist invents a time machine, and then has to go back in time and prevent an earlier version of himself from giving it to a Corrupt Corporate Executive. The original versions of the scientist and his girlfriend end up dying while the "earlier" versions of them manage to keep the time machine from falling into evil hands.
 * The host segments also play around with this trope, with Crow going back in time to prevent Mike from getting shot into space. Unfortunately, Mike dies in this alternate fate-line and his Jerkass older brother Eddie ends up on the SOL instead. Crow goes back in time again to tell the earlier version of himself not to warn Mike, and, as a result, the earlier version of himself gets stuck in the past where he will presumably remain, as an employee of the cheese factory where Young Mike worked.
 * There is a sort of this in Seven Days. It's stated that simply backstepping (Going back in time one week) already changes the timeline because the Sphere materializes and changes air currents, causing airplanes to land a bit sooner/later and the like. Of course, it was never explained further than that.
 * Hysterically parodied in a The Whitest Kids U' Know sketch. Every time Trevor and Sam try to change history, random things happen (because that's how physics works). They go back in time and kill Hitler; JFK turns into a panda bear. They stop two Godzilla-esque monsters from attacking each other and cause the Vietnam War. After preventing 9/11, one of the character's sister starts to disappear from a picture (a parody of Back to the Future). In response, they scream "We have go back and save 9/11!" Seems the maker of the show didn't know anyone close to the attack.
 * A big part of Heroes, where time travel (mainly by Hiro Nakamura, and later ) and precognition are used to fix, worsen, and then repair the future many times. Featured most prominently in the episode, "The Butterfly Effect", where Future Peter screws up the past so badly, that he leaves things for Present Peter to fix since he had "stepped on too many butterflies."

"Martha: "But, isn't it dangerous? You know, like you step on a butterfly and the future's completely changed because of it?"
 * Possibly subverted, or at least morphed into You Can't Fight Fate, during Volume 4 where.
 * Heavily subverted with Charlie. Through Hiro's intervention, she is saved from her brain tumor and Sylar's murder-spree. But she is kidnapped and stranded in the 1940's in order to manipulate Hiro. Before she went, she was an insatiable reader and had the super-power of 100% perfect memory - someone with enormous potential to alter history for good or evil. Yet she does...nothing, instead choosing to work a factory job and settle down.
 * Supernatural covers this in two different episodes, although they aren't played straight. In one, Dean is tricked into believing a Djin has taken him to an Alternate Universe where his mom never died, and none of his family members became Hunters. Everyone's living happily, but as a consequence, his relationship with Sam is estranged because of their lack of time together, and all the people he saved as a Hunter died in their "accidents" without the brothers there to prevent them. Luckily, it was All Just a Dream. In the second episode, Dean is actually taken back into time by Castiel, who warns him that any attempt to save his mother will inevitably result in the death of the innocents he has saved. Subverted in that no matter what Dean did, things ended up going exactly the same way anyway.
 * In Smallville, Clark goes back in time to save life. However, in preventing the accident,, no longer having a reason to stay and console Clark, goes straight to his meeting with . The scuffle that ensues causes him to have a heart attack, ultimately killing him.
 * Several alternate universe/timeline episodes of Stargate SG-1 feature worlds where it seems like only one small thing has changed, but often, that leads to something even more horrible happening. A good example is "2010", where contact with one group of aliens lead to.
 * In the Doctor Who episode "The Shakespeare Code", the Doctor lampshades this to put Martha at ease in her first time time-traveling.

The Doctor: "Well... I tell you what then: don't step on any butterflies. What have they ever done to you?""


 * While the show is mostly immune to this trope, with characters messing through time willy-nilly, it is used occasionally. The episode "Turn Left" is probably the most striking example, with an It's a Wonderful Plot twist.
 * "The Fires of Pompeii" both plays this straight and subverts it. Donna asks the Doctor why he can't warn the city of the impending volcanic eruption, only for him to say that it's a fixed point in time that must not be tampered with. At the end, as the volcano is erupting, Donna pleads with the Doctor to help, so he rescues one family (the one they've gotten to know throughout the episode) and puts them outside of the city with what appears to be no consequences.
 * The Doctor has mellowed a bit when it comes to messing around with history. The First Doctor story An Unearthly Child has him so paranoid about the possible ramifications of this trope that he is convinced that the mere idea that a device such as the TARDIS exists could irreparably change the course of human history.
 * In the episode "Father's Day", Rose goes back in time to visit her father before his death but ends up saving him from his fatal accident. The resulting tear int he fabric of reality lets through a host of aliens who feed off time energy and kill a lot of people.
 * In the season six finale, River Song tries to subvert reality by . The result of this is that all of time and space coexist in the same eternal instant, with anything unable to happen until the proper events of the timeline are carried through.
 * Used in the UK series Misfits, where Curtis uses his time-travelling ability to go back to the night he and his girlfriend Sam were arrested for drug possession. His initial attempts to change things only make things worse (such as Sam ending up stabbed by the dealer), but he eventually manages to change things enough that neither of them are killed or arrested and "jumps" back to the present, where it looks initially like an inversion; he's back to being an Olympic athlete and Sam is alive. Then he realises that without him there to save him, almost the entire main cast were murdered back in the first episode.
 * A continuing theme of the Cut Short series Odyssey 5. Five astronauts who survived the destruction of Earth are sent back in time five years to try and avert the xenocide. Although they agree not to try and change their own personal lives none of them can resist trying to tinker with events, with varying results.
 * The Kamen Rider 40th anniversary movie Let's Go Kamen Rider is all about this. OOO and Den-O chase a monster back to the era of the original Kamen Rider and accidentally leave behind an O Medal. When they return to 2011, that single Medal has allowed villain organization Shocker to Take Over the World and put four decades' worth of Kamen Riders on the ropes.
 * Fringe: In a roundabout way, the show reveals in bits and pieces that the entire plot of the series and the fate of multiple universes all pivoted on a single inadvertent action by a time traveler: . This miniscule action caused . This dimensional mess destabilized the physical laws of both universes and jeopardized the timeline that would spawn the time-travelers in the first place, forcing them to take a direct role in correcting the original mistake.
 * The Community episode "Remedial Chaos Theory" is all about this. It's decided that a roll of the dice will dictate who has to leave and pick up a pizza, so the one rolling the dice will be creating six different universes, all based around what the characters would or (or in some cases, wouldn't) be doing in the two or three minutes that the pizza is getting picked up. All outcomes except for one involve the group somehow creating a conflict in these couple minutes. In the real (best) outcome, In the "Dark" outcome  Abed acknowledges that it's the darkest timeline, and makes everyone felt goatees so they can all be "evil" versions of themselves.
 * Angel. In "Birthday" the demon Skip shows Cordelia (with the help of Monday Night Football replay and onscreen graphics) how her life could have been different if she'd just moved in one direction as opposed to the other during a party in the series premiere and met a Hollywood talent agent instead of the series protagonist, becoming the famous star of a comedy television series instead of a Fainting Seer whose visions are killing her.

Music

 * The butterfly-as-misfortune motif is used in the Vocaloid song Butterfly on Your Right Shoulder.
 * In another Vocaloid song ANTI THE∞HO Li C, black butterflies are used and seen throughout the song in many ways. The song is about the ignorance of people, though, and how poor a world they can create with their own stupidity.

Radio

 * In Ray Bradbury's radio drama, A Sound of Thunder, there is a "Time Safari" where you can go back in time and hunt any animal. It is a Defied Trope here because they specifically look for animals who are going to die and go back in time to just before they do, and have an anti-gravity path to shoot the animal from.  This is a Trope Namer; the other Trope Namers drew inspiration from this one.

Tabletop Games

 * Averted in Feng Shui, where the universe actively resists attempts to change it. To illustrate it, the sourcebook gives the classic example of a man going back in time to kill his own grandfather. If Johnny Fong goes back in time and kills his grandfather, he returns to the present to find that his name is Johnny Wong now, but nothing else has changed. In Feng Shui, world history bows to the whims of the people in control of the world's feng shui sites, and anything done by insignificant time travelers just gets corrected.

Video Games

 * Prince of Persia: Warrior Within actually uses this trope, but with a twist -- instead of unexpected consequences, there is an actual guardian of time that hunts the Prince in order to restore time to its original flow.
 * Played straight in Prince of Persia: Two Thrones where the events of Warrior Within have undone the events of Sands of Time
 * This is pretty much the entire premise for the DS game Time Hollow. Where the player makes small changes to the past and watches the subsequent results.
 * This is also the plot for the Play Station 2 game Shadow of Memories which was written by the same maker of Time Hollow. Dude loves his time travel.
 * The basis for the Red Alert series. The whole thing started when Einstein went back in time to kill Hitler, resulting in WWII taking place between the Soviets and the Western Allies.
 * And in Red Alert 3, the Soviets go back in time to erase Einstein in order to save the Soviet Union, weakening both the Aliies and the Soviets(no nukes) and creating the Empire of The Rising Sun, resulting in a three-way world war.
 * Blaz Blue. Six words: The Wheel of Fate is Turning.
 * Rebel 1!
 * Action!
 * Achron allows for rather odd situations involving chronoporters (time-teleporters) and battles. For example, by sending units back in time to fight alongside themselves, if the original units are damaged in the ensuing battle, the future versions will be also damaged when the next timewave comes by. Eventually, this can resolve into a much weaker army than was originally used. Also, these sorts of time-manipulation tricks can allow for armies to go back to attack economic or production structures to disrupt opponents. For example, killing that one marine who built all the resource processors that made the construction of the army that's harrassing you in the future even possible. So, by killing one marine, you defeated an entire army. It should be noted that much of the game is built on these sorts of tactics.
 * It should also be noted that it's not segregated to the story: you can play with these temporal shenanigans yourself. In multiplayer.
 * Averted by Chrono Trigger in that, while major changes to the timeline (such as the entire plot of killing Lavos) will, of course, have major effects, minor things, such as opening a treasure chest in the past, will, at most, have the effect of making the corresponding treasure chest empty in the future, yet you can get the future chests, then go back in time and open the past ones with no consequence... Killing monsters doesn't do a thing; they'll even reappear when you enter the area.
 * Mortal Kombat 9. By doing some minor things to avert a Bad Future, Raiden ends up making his and Earthrealm's future doomed. For instance,
 * Used for a joke in Metal Gear Solid 3: Snake Eater where there's a point in the game where you can kill the young version of future turncoat agent Ocelot. Doing so ends the game instantly, with the game telling you that you created a time paradox.
 * Timesplitters: Future Perfect subverts this trope with Cortez causing countless paradoxes and shooting up everything. After all, he is cleaning up the mess of the actual villain. By the end, he manages to destroy the Timesplitters that had made a mess of the timeline, fixing up his own future. It's possible that all his deeds were always meant to happen or were simply erased from existence.
 * Also subverted in Onimusha 3: Demon's Siege. Samanoske is stuck in present day and can therefore not affect events in the timeline, but Jaques in ancient Japan can and has to due to the Genma mucking around with time travel and causing the current mess in the first place. The two end up being time janitors, in a way.

Web Comics

 * In the now likely defunct webcomic Adventures of John and Dave, Dave goes back in time about three weeks to play a prank on Air Force One and finds that this caused Germany to win World War II.
 * Something Happens has some fun about it here.
 * In Sinfest, Squidly calls a butterfly a murderer for producing such effects, and then imagines his own effects.

Web Original

 * The Alternate History Forum, home of Look to the West and Decades of Darkness among others, is divided on the issue. There are purists ("step on a butterfly and everything changes") and non-purists ("consequences of an event ought to follow on logically: things take a while to change, and sequences of reasons can be made"). People who don't include any "ripple" of changes are laughed at. To quote veteran member Jared "In 1618, Australia will be discovered on time and the effects [of a sedentary yam-farming aboriginal civilization] will spread. Anyone asking "Great! How does this changed Australia affect World War 2?" will be fed to the blobfish."
 * This is parodied in Reds, where the alternate history version of the Alternate History Forum appears, and the members discuss the alternate timeline... and the exact same kinds of arguments crop up.
 * Played with, and ultimately subverted, in Red vs. Blue: Church gets transported a thousand years into the past and then uses the time to come up with plans to prevent the accident that caused him to travel through time in the first place. The loop repeats dozens of times but everything he tries never changes anything.

Western Animation

 * Time Squad: Planet of the Flies, a Parody of Planet of the Apes. Tudrussel squashes a fly in the Stone Age, altering history so that the world is ruled by giant flies. Complete with a ruined Statue of Liberty scene. "You maniacs! You blew it all up!"
 * Phineas and Ferb: "Phineas and Ferb's Quantum Boogaloo" featured an adult Candace going back in time to bust Phineas and Ferb for the rollercoaster and returning to her own time to learn it was now a Bad Future. As it turns out, her effort to bust her brothers not only created a wave of child-proofing hysteria, but it caused Perry the Platypus to get injured by Dr. Doofenshmirtz's evil scheme backfiring, instead of Doofenshmirtz like in the original timeline. This allowed Doofenshmirtz to ride the wave of hysteria and take over the Tri-State Area, turning it into a ruined industrial dystopia where fun and creativity are outlawed, kids are kept in People Jars until they reach adulthood, and everyone is forced to change their name to "Joe".
 * In the legendary Simpsons Treehouse of Horror segment "Time and Punishment", a malfunctioning toaster transports Homer to the prehistoric past. He remembers some Genre Savvy advice Grandpa gave him regarding this very trope, then instantly forgets it to squash a bug. When he returns to the present, Flanders has taken over the world. And his attempts to fix the timeline cause alternate futures that range from even worse to just plain weird...
 * When one of his sneezes causes all of the dinosaurs to drop dead, he moans, "That's gonna cost me."
 * In Futurama's first movie, Bender's Big Score, time travel plays a huge role in the plot. There's even mention of a failsafe in the universe itself that erases impossibilities created by time travel, like the same person meeting themselves, that prevents the Butterfly effect from having a dangerous effect. It comes up again in an episode where the Professor makes a time machine that only travels forward in time
 * In "Roswell That End's Well", they go back in time to become the Roswell Incident. When Professor Farnsworth finds out that Fry's grandfather is there he gives him the classic advice for people going back in time: "Don't do anything that will change history. Unless, you're supposed to do it, in which case for the love of God don't not do it." Of course he does by killing his grandfather but the effects are minimal because