Off the Rails



"I kill Gandalf."

- Igor (while roleplaying The Lord of the Rings), Dork Tower

The Game Master has created an epic plot that spans time, space and dimensions. Its scope is exceeded only by its elegance, its elegance only bettered by its plot, its plot only bested by its setting, and the whole thing is held together by a compelling supporting cast of NPCs. The campaign is perfect.

...at least, that's what the Game Master thinks.

Meanwhile, the players have decided that the huge scope has made the world shallow, it's only "elegant" if you like a Cliché Storm, the plot was lifted straight from the third remake of something, the setting looks like it came from Manos: The Hands of Fate with the Serial Numbers Filed Off, and the so-called supporting cast of NPCs are either cookie-cutter stereotypes or Mary Sues who make the players feel like the supporting cast. It's about halfway through the campaign, and the players have decided that everything is only going to get worse. The time has come to strike a blow for freedom, for better plots, and against this idiotic Game Master. The players go Off the Rails.

This can take many forms, but at its core, one (or more) players disrupts the Game Master's carefully-crafted plot by killing an important NPC, revealing an important secret, or just refusing to go where the plot demands they should go. Or maybe they just switch sides.

If the Game Master is inflexible, either the GM ignores all actions that disrupt his plot (a.k.a. Railroading), or drops a whole ton of rocks on them. Or pauses the game to confer with his players about them ruining the adventure. A more creative Game Master, on the other hand, will take this player revolt and run with it, spinning a new plot out of the threads of the player's actions. Of course, good Game Masters rarely have their players revolt on them in the first place. A party going thoroughly and maliciously Off the Rails is often a herald of the end of the gaming group, or at least the end of one person's tenure as Game Master. Alternately, if there's just one player who's dissatisfied and he keeps grabbing the throttle and gunning the train, that player's character may be subject to a lightning bolt on a cloudless day, or sudden violent chest pains, or a drive-by mauling by a mind flayer that leaves everyone else untouched. (Or the other characters may just kill him or her.) The Henderson Scale of Plot Derailment has been invented by 1d4chan (the wiki for all things /tg/) to measure just how far off the rails a game can go, named in honor of the legendary Old Man Henderson.

This trope is effectively the player's version of Rocks Fall, Everyone Dies. Compare Total Party Kill, where the game-ending disaster comes from incompetence rather than malice or loss of control over the game. Note that this doesn't apply when there were no rails to begin with.

Occasionally, the train can be put back on track (any track) with a little help from Schrodinger's Gun and copious amounts of improvising. The winners in this situation are usually all involved.

Compare to Screw Destiny, where characters decide to go Off the Rails on a more cosmic scale.

Not to be confused with Derailing, which is what happens when someone wants to forcibly change a discussion topic or others' plans, or Plot Detour, which can form part of an attempt by an author of a campaign to spin out the story through misdirection or change its direction.

Film

 * In Addams Family Values, Wednesday does this in the middle of a Thanksgiving play while playing Pocahontas. After citing the future transgressions made against the Native Americans, she burns the "pilgrim" cast at the stake.
 * Maximus in Gladiator manages to derail a gladiatorial reenactment of a battle (that his side should have lost). It's even Lampshaded by the emperor.
 * In Mazes and Monsters, Jay Jay ruins his group's current campaign by having his character jump into a spike pit. He does this with the express intent of starting a new game, with himself as the Game Master, to make use of his idea to LARP in the local steam tunnels.
 * Spoony lampshades this in his review of M&M, pointing out the GM's Thousand-Yard Stare as the mark of a Dungeon Master who's fully aware that his entire game has just gone Off the Rails (he even uses this exact term).
 * A near-literal case in Tron. During the light-cycle game, one of Sark's Mooks crashes into a wall, de-rezzing, but leaving a glitch in the wall's side. Flynn decides "what the hell" and runs straight for the glitch, escaping the Game Grid. Tron and Ram think he's completely glitched, but decide he might just have the right idea.
 * In The Cabin in the Woods,.

Literature

 * The book 'The Munchkin's Guide to Power Gaming' features another hypothetical example, in which a GM wants the players to go into a dungeon, but 'all they want to do is find out what's down the road from the dungeon entrance'.
 * Honor Harrington telegraphs much of the plot if you understand what the story is based on. Then someone goes ahead and nukes Napoleon...

Live Action TV
"Janeway: Master da Vinci doesn't like visitors after midnight.
 * This Robot Wars fight. A 4-way free-for-all begins with . Hilarity Ensues from there. Outrageous stuff from the fight includes . The result is eventually decided when, leaving what's left to move on. "What's left" being "Not much".
 * Weaklings. Another match involved a one-on-one fight between two robots. One won almost immediately, flipped both House Robots and was only caught out by the Flipper randomly going off midmatch.
 * What about the numerous times when Razer celebrated winning a match by trying to destroy one or both of the House Robots?
 * Star Trek: Holodeck simulations in Star Trek were often portrayed as futuristic LARP. As such, characters (In-Universe) would occasionally go Off the Rails by doing things that seemed logical to them but didn't make sense within the simulation.
 * In the Voyager episode "Night", Tom Paris has Seven of Nine play a Damsel in Distress in his Captain Proton simulation who gets captured by Satan's Robot. Instead of following the plot, Seven takes the most logical route, opens a convenient hatch on the robot, and pulls out its wiring.
 * It goes really Off the Rails in Bride of Chaotica! when.
 * Likewise when Seven uses the Leonardo da Vinci holoprogram for a little time to herself.

Seven: He protested. I deactivated him."

""Well, that's that sketch knackered then, isn't it?""
 * In the Star Trek: The Next Generation episode "Qpid", Q drops Picard in the middle of a Robin Hood fantasy-world and tells the captain that if he doesn't rescue Maid Marion (who is his Love Interest, Vash), she's going to be executed by Sir Guy of Gisbourne. Both Q and Picard are quite surprised when the eminently practical Vash agrees to marry Sir Guy, as it makes more sense than some stupidly heroic rescue plan.
 * Another TNG example: in the episode "Elementary My Dear Data", mere minutes after Geordi and Data enter a Sherlock Holmes holo-novel, the plot begins when a man supposedly attacked turns up with a policeman. Data at once solves the entire case (which is supposed to be the length of a full novel or a film) by firing a short barrage of questions at the man and ripping open his jacket to reveal evidence that he is a counter-agent. He was remembering how the original novel went. Unfortunately, he had read all the original novels. Geordi storms off. The next time goes no better because the computer attempts to simply pastiche elements from the novels, and (let's repeat) Data had read them all. The next time they try a holo-novel, they accidentally ask the computer to create "an adversary capable of defeating Data". Cue virtual!Moriarty, a holodeck construct capable of interfering with the basic systems of the Enterprise. Cue mass Oh Crap from the crew.
 * In the DS9 episode Our Man Bashir featuring a James Bond pastiche, Bashir's character helps the villain destroy the world, and the poor computer almost has a nervous breakdown trying to keep the simulation running. Probably why they came up with the Vic Fontaine Holo-Programme, which was designed to operate off the rails, and only caused a major problem when its actual story arc kicked in and it stayed on them.
 * Kira apparently hit Lancelot when he came on to her in King Arthur game where she was playing Guinevere. She was playing a married woman, after all.
 * Q once created a scenario where he and Sisko were in a boxing match and Q was being his normally chipper self, playing around until Sisko just decked him to the floor. Q was stunned, as he was used to the arguing matches with Picard, and quickly reverted everything back to normal.
 * In The Young Ones, an attempt to parody the cheese shop sketch from Monty Python's Flying Circus is immediately brought to a halt when the shopkeeper notes that the shop is not a cheese shop. Alexei Sayle's response:

""I see what your problem is! You're confused by their names, because they all sound like questions!""
 * Michael Palin did this himself during performances of the infamous " Dead Parrot Sketch", in an attempt to throw John Cheese off as well as add spice to an old gag. In their live performance at Drury Lane, when John asks if the slug replacement talks, Palin answers with a prompt "Yes." There's a brief pause, and then Cheese responds, "Right; I'll have that one then."
 * One sketch on At Last The 1948 Show involves an educational segment where four actors teach basic English vocabulary, and one distraught, underpaid actor (played by John Cleese) derails the segment completely by inserting bogus words into his lines, vandalizing the set and pouring scalding hot tea on the heads of his co-actors.
 * Good News Week. The show was supposed to go from 8:30 to 9:30, but they always ended up getting distracted by a humourous aside or five. Now it's supposed to go until 9:45, and usually finishes around 10:05. Wanna know why?
 * As of 2010, the show is supposed to go until 10:00, and it's still overtime.
 * Whose Line Is It Anyway?'s Irish Drinking Song about "yelling the wrong name in bed". Meow.
 * In the Myth Busters MacGyver special, Adam and Jamie are put through a series of challenges to test their MacGyvering abilities, set up by Tory and Grant. The final challenge involved creating a signal that could reach a certain height. Tory and Grant set up the surroundings to provide all of the materials needed to build a potato cannon, which results in quite a surprise when Adam and Jamie build a kite instead, using the rope that they were tied up with at the very beginning of the segment.
 * In another episode, Adam and Jamie made a challenge for each other: to build home-made hovercraft using household materials and under a budget and have a race with the machines they build. Both at first conform to the rules. Then Adam begins cheating. He ends up spending twice the budget on a truly ungainly "hovercraft" that requires him to flap his arms around while wearing press board "wings" and getting pushed by assistants to the goal line.
 * Match Game was designed around the celebrities appearing to go Off the Rails, but the School Riot was a rare actual example.
 * Kids in The Hall: the "Bad Straight Man" sketch, in which Dave utterly ruins the "Who's On First?" routine.

"Richie: "You know my great watch gag? Well I've forgotten to put it on."
 * Survivor: Redemption Island was hyped up as a grudge match between two well-known returning players, Russell and "Boston" Rob. But Russell's tribe knew he would backstab them for the lulz the first chance he got, so they threw a challenge in order to vote him out almost immediately. Unfortunately, this meant that Rob went unopposed for the rest of the season, as the other tribe gave him their Undying Loyalty.
 * On the October 9, 2009 episode of the Japanese quiz show Super Time Shock, in the first round of the tournament, all 6 contestants in the D block got the exact same score. This was the first 6-way tie in the history of the show since the original Time Shock premiered in 1969. Evidently nobody thought this could happen and the show was unprepared for such a scenario, as they ended up having to break the tie using Rock-Paper-Scissors.
 * Bottom Live 2 gives us this exchange:

Eddie: "Well, that's shagged that, then!""

Tabletop Games

 * There are a great deal of stories of clueless players derailing Shadowrun games available at The C.L.U.E. Files. Fine reading for anybody who enjoys dumb player stories.
 * A legendary example is the story of Noh. A DM had his players, on a spiritual quest, encounter what he thought would be a simple virtue challenge: a powerful magic rapier and magic chain shirt on a pedestal, guarded by a little girl (actually a spiritual construct). The little girl could only say two things: "No" or -- if a "No" answer would be misleading -- "Please do not take these items". The party spent fifteen minutes talking to her, assuming she'd suffered trauma of some sort. Then the bard played a song to see if he could get a reaction from her. He rolled high, so the DM let the little girl shed a Single Tear. The party's response: they fell in love with her on the spot, declaring her the cutest thing ever and deciding to keep her. The little girl kept going back to the items, so the party eventually went back, gave them to her, and then took her with them. The DM, conceding defeat, arranged for her to gain a mind of her own, and the party made her their mascot, naming her Noh (as that was her response when asked what her name was).
 * And they completely ignored said items in favour of Noh. Those are D&D players we are talking about, so such a reaction is a Crowning Moment of Heartwarming by itself.
 * What happens when a player decides to tell the GM's Marty Stu to talk to the gun? Read the saga of "Fuck you, Strake!"
 * The RPG Spirit of the Century makes a point of encouraging the GM to run with any derailments by making highway systems rather than railroads and paving as they go. On the other hand, it does allow you to offer Players rewards for having their character perform actions suggested by the GM, so long as it has something to do with the character's Aspects, which the Players choose to begin with.
 * Inherent in Paranoia to such a degree that many GMs recommend not installing the rails in the first place. (Especially since by the first 'station', everyone will probably be dead.)
 * On the other hand, if the GM really really wants the characters to be at Point X, all it takes is one order from The Computer, and they are being frog-marched X-ward by a heavily-armed Vulture Squadron "escort".

Theater

 * The musical Pippin ends when Pippin refuses to obey the Leading Player's 'script' and light himself on fire. The Leading Player doesn't know what to do, so he basically ends the show, after having a giant breakdown.

Video Games
"Go to early, or
 * Morrowind readily allows the player to break the main quest by killing any of dozens of plot-significant NPCs, and from there just troll around endlessly in the Wide Open Sandbox. There is, however, still a "back-path" to finishing the main quest if you decide to save the world after you've done everything else.
 * Morrowind's sequel Oblivion does not follow in the same vein as Morrowind; important NPCs are simply "knocked out" briefly.
 * To alleviate the issue, the game warns you if kill someone vital to the Main Quest ("the threads of prophecy have been broken"). The bad news is that the ability to remove Essential status from an NPC through scripts was introduced in Oblivion, and the warning was not removed with the status, so the game warns you even if killing the NPC will no longer cause the plot to go off the rails.
 * In Neverwinter Nights, it is theoretically possible to slaughter the entire population of the city of Neverwinter...except for Aribeth, who is totally indestructible and doesn't react to anything you do other than talk to her.
 * This may not be the best example, as some shop owners can glitch to be invincible, and then follow you (EVERYWHERE, even through doors), attacking you till you die.
 * Not necessarily an example, but there are instances in old Super Robot Wars games where you could do this, either by defeating all enemies at a level currently before reinforcements arrived (they would come on a specific turn and not earlier, so if you cleared the level before then, you'd just skip those fights).
 * Many games also have bosses who will unleash particularly unpleasant abilities, almost always including restoring their health to full, when they're hurt badly enough. However, the earlier ones can't handle said bosses being killed instead of dropped to low health, and they simply die early despite having the ability to restore themselves.
 * There are examples of this in very early games, however. In Super Robot Wars 2, destroying Cecily's mobile suit near the end will prevent her from appearing again as an allied NPC later on. In Super Robot Wars 3, certain cutscenes can be skipped outright with the proper application of force on bosses when the game expects you to just destroy mooks. And then there's F/Final, where even Angels can be killed prior to their intended death scene.
 * Portal and Portal 2 are both linear games. The plot, however, involves you going completely off the rails with respect to whatever plans the AI Mission Control has. In the first game, you escape from GLaDOS' Death Trap and wind up literally taking her apart in order to avoid her vengeful wrath. In the sequel, it happens no less than three times: first, when Wheatley derails GLaDOS' plans to murder you; second, when Wheatley manages to derail his own plans before they even get started by ; third, when you escape Death Trap in "The Part Where..."
 * The game I Have No Mouth, and I Must Scream makes this an intentional example. AM, the maniacal AI that puts the characters into each situations expects the characters to give into their weaknesses. If the players proceed to conquer their Fatal Flaws and prove AM wrong, then this enrages him so much that it will initiate a Logic Bomb; then the characters are given the opportunity to take down AM once and for all.
 * It's a Running Gag in Nippon Ichi games that, if you try to go Off the Rails by winning a Hopeless Boss Fight, the world often gets destroyed. Since you kind of need the world to continue the story, you have to start all over again.
 * Fallout 3's plot involves talking to about a dozen NPCs, each directing you to the next NPC, until you meet the one person who can unlock the door to . A faster way involves trading your only weapon for lots of ammo crates (each filled with 1 bullet) and building a big staircase out of them to get past the locked door.
 * You can also accidentally skip the first main plot quest or two if you -

Go to early, or

Go to early, or

Skip straight to  if you already know how to find any of these places."


 * The developers did anticipate a couple of these skips. If you already know where your father is when talking to Three Dog, then the reward for finishing his quest will change from Three Dog telling you where your father went to Three Dog telling you where a weapons cache is located.
 * Fallout: New Vegas has a few major factions that you can ally with to complete the game. Performing quests for each faction may make opposing factions warn you that they'll stop accepting your support if you persist in helping the other factions - if you continue, you'll no longer be able to progress in their missions (though they will remain non-hostile as long as you don't). You can then make all three major factions mad at you - possibly by meeting with their leaders, killing them, and eating their corpses - which will give you a special perk. This leaves you only one way to beat the game - going off the rails the three factions built and taking over Vegas yourself with the help of . Unfortunately, it's impossible to go off this rail since   is more or less immortal, and doesn't even care if you open fire on him repeatedly
 * The Nameless Mod includes a few ways for the player to go off the rails, including.
 * Specifically, Trestkon as the PC.
 * Additionally, should Trestkon.
 * There's a point in Deus Ex where you are ordered to kill an unarmed NSF higher-up (Juan Lebedev) who knows a lot about what's going on -- and is willing to tell the player. Halfway through the explanation Anna Navarre will show up and order you to finish the job. You can either refuse (Anna will kill him and get annoyed with you) or do the job yourself -- or.
 * It's that the game in no way suggests that this third way is an option and it's entirely up to the player to decide to  that really sets Deus Ex apart from other 'non-linear' RPGs.
 * However, most plot-critical NPCs are invincible until they've outlived their usefulness to the plot. For example, Walton Simons, Joseph Manderly, Anna and Gunther are all invincible until . However, you can kill Maggie Chow before you even speak to her.
 * The sequel does this much more. The player can kill anybody they have access to, assuming they have at a functional weapon on them, no matter how important this person is, and the plot adapts. In fact, at one point you can trap two characters who the global society depends on in a room, and irradiate them to death.
 * All of the Disgaea games have at least one ending like this.
 * Pass the bill in Disgaea 1, and you'll get an opportunity go invade   instead of moving on to  . This leads to a couple mildy difficult encounters, followed by a final showdown where
 * "Etna Mode" from the PSP/DS remake is all about this, since it's about what would happen if Laharl died at the beginning of the game.
 * Defeating Laharl in one of Disgaea 2's Hopeless Boss Fights treats you to an ending where he blows up the planet in retaliation.
 * Replaying the stage where you fight  Mao's father in Disgaea 3 nets you an ending where pretty much none of the plot threads are resolved.
 * If you kill Feinne the first time you encounter her in Soul Nomad and The World Eaters, this leads to a fight with Asagi, who blows up the planet after beating her (it's even lampshaded by Gig). is something of a campaign based solely around this, since it begins with
 * An in-universe example of sorts takes place in The Reconstruction, but not by the main characters. Throughout most of the game, . But then.
 * Golden Sun: Dark Dawn is basically about your quest being derailed by the bad guys, who have their own agenda they want you to fulfill. Your Psynergy Vortex business can wait, right?
 * JFK: Reloaded is all about you trying to recreate the JFK assassination. But what happens if you decide otherwise?

Web Comics

 * Happens far too many times to count in Dork Tower, usually due to their overzealous gaming strategies.
 * They once had a game based on Lord of the Rings. The campaign opened with Merry killing and gutting Gandalf, Pippin beating Frodo to death... they were planning to institute a military draft in the Shire when Matt (the GM) went catatonic.
 * In the second attempt, one of the players is assigned to play Gandalf... but with his abilities limited to talking to birds and casting fireworks. The players ended up using Gandalf as a Bulletproof Human Shield and battering ram.
 * Another session ended with the players having taken over the kingdom, forged an empire, and conquered all of the known lands... when their goal was to just rescue the princess.
 * One strip had Matt crying to a friend about how his characters had not only derailed his adventure by killing everyone, they had also summoned Elder Gods to destroy the game universe. They had been playing Bunnies and Burrows (a game where all the characters are normal, mundane rabbits).
 * Darths and Droids imagines Star Wars as a tabletop RPG in a universe where the films never existed. The entire plot of all six movies comes about because "Qui-Gon" and "Obi-Wan" go Off The Rails during the first five minutes of Episode I.
 * Another example happened offscreen in a fantasy campaign they played between the first and second movie, when the characters let their Munchkin be killed by the main villain, left him dead, and after they killed the villain resurrected him and joined his side.
 * Another offscreen example in a campaign with Annie as the GM. Her planned campaign would've been the plot to the Twilight series, but the players, with their Kill'Em All mentality at the first sight of vampires and werewolves, turned it into the plot for Van Helsing.
 * A couple of the "alternate" strips go Off the Rails:
 * In Magicians & Munchkins, everybody decides to be a Min-Maxing Munchkin, including the GM, whose Final Boss is an all-powerful Wicked Witch with the drawback of "Vulnerability to Water". Which the players accidentally discover 3 Sessions earlier than the GM intended them to.
 * In Trenchcoats & Turncoats, Ilsa and Victor are Dirty Communists who steal the plans and escape on the plane because Jim (as Rick) is dumb enough to believe their cover story that they're Americans despite the facts that Annie (as Ilsa) speaks with a thick Russian accent and Sally (as Victor) only speaks in stock Russian phrases. But what really gets the GM frothing at the mouth is that he'd intended the campaign to be an epic, exciting, globe-spanning adventure but the players hardly ever left the bar where they all met in.
 * By contrast, the webcomic that inspired Darths and Droids, DM of the Rings, features a scenario where every single attempt by the players at getting Off the Rails is met by either failure or cruel retaliation on the part of the Railroading GM.
 * The DM does face a problem when early on. And later on they even get to.
 * In a smaller example, Gimli's player manages to derail Gandalf's battle against the Balrog by pointing out that it would be against their alignments to squander the Heroic Sacrifice, meaning the Final Speech the GM had written up for that scene goes unused while the Fellowship legs it.
 * Irregular Webcomic has two of its storylines being characters in roleplaying games. When time travel is introduced into both storylines, the PCs quickly disrupt the timeline, preventing events that for them have already happened from happening, resulting in paradoxes that contribute to the destruction of all reality. It should be noted that the DM was dead at the time (his disappearance is noticed in the "Space" storyline), so he was unable to prevent this catastrophic derailment.
 * In Burning Stickman Presents...Something!, one of the protagonists knocks the plot, which had been a retelling of Mega Man X 4, off the rails by.
 * In Homestuck, a number of events have conspired to doom the kids' Sburb session: Jack, who was meant to offer a means of helping the players dethrone the Black Queen before the Reckoning, gained access to a.) a weapon of unbelievable power and b.) nigh-omnipotence, and immediately began to destroy not just the Sburb session he originated in but also other sessions. Having learned that their game was doomed, Rose searches for a way to break the game because winning it in the traditional fashion is no longer possible. It appears that, in the future, she is ultimately successful.
 * After scratching the original session, the new Alpha session is already going Off the Rails before the game even starts. The agents of Derse are killing dreamselves before the game in violation of the normal rules, and someone has repeatedly tried to assassinate Jane on Earth.
 * A very common plot seen with the Knights of the Dinner Table comics. In some strips they manage to go off the rails before the adventure starts because they refuse to listen to they guy who's supposed to tell them what the adventure is. In one, after they've stolen the king's silverware during a banquet and therefore had a huge battle with the guards rather than be sent on a quest, B.A. finally storms off after Bob says the adventure was much better than he expected, and Brian recommends he get the other modules in that series.
 * Happens quite a lot in Full Frontal Nerdity. A(nother) good example would be this.

Web Original

 * Things Mr. Welch Is No Longer Allowed to Do In An RPG is a long list of attempts by somebody who seems to be the Casey Jones of games gone off the track.
 * Several times in Ruby Quest. They were not supposed to smash their way into that medicine cabinet with a crowbar. Because they'd gotten in, they could tranquilize Stitches instead of killing him, and they then stuffed him in a healing locker with the photograph of everyone standing around happily for when he wakes up. Weaver also hadn't even considered that they'd try to save  or . All of which actually gave them a better ending. Putting the hand in the pneumatic tube, however, was just silly.
 * Spoony's story about Vegan Steve and the Deck of Many Things is a living testament to this.
 * In a Vampire: The Requiem LARP, Spoony's character was forced into joining the local Church Militant sect. His response was to use his character's extensive knowledge of Chemistry to produce enough plastic explosive to level a city block, then snuck it into the local Prince's sanctum.
 * Spoony also tells the story of a Star Wars game he ran, where he decided to have Darth Vader cameo...which, unfortunately for him, inspired the players to completely abandon their previous mission and focus entirely on trying to kill the Dark Lord of the Sith. He says this taught him the hard lesson that you do not include established characters in an RPG, lest such an event happen.
 * In his "Thieves' World" story, Spoony relates the tale of a campaign that accidentally went off the rails when a character impulsively flung an acid flask at a figure entering through a door in a cultist's lair - and ended up hitting the party's benefactor, a semi-immortal champion of the setting's god of war, critting him and burning half his face off. What follows becomes a Crowning Moment of Awesome for both Spoony as a DM and for his players, as he rewrites the campaign around this moment to turn the benefactor into the Big Bad, and the players eventually organize a peasant army against him and his minions.
 * Seen in Tales From the Table as early as the first episode.
 * Often gets posted on /tg/, especially when GM's original plot was massively retarded for some or other reason (usually it's blatant dive into Magical Realm, GMPCs and/or failure to make sense) and the resulting clusterfluffle happened to be hilarious.
 * Special mention must be made of the tale of Old Man Henderson, "The Investigator who won Call of Cthulhu." To make a long story short: A group is incredibly fed up with the Keeper of their Call of Cthulhu game, who is not merely a Killer Game Master, but also incredibly uncreative in his methods of TPKing. Thusly, one of the players creates Old Man Henderson, a drunken Scottish nutcase who falsely claims to have served in Vietnam and has joined the Investigators due to a mistaken belief that the Cult of Hastur has stolen his lawn gnomes. (he actually donated them to charity, but passed out in a drunken stupor afterwards and doesn't remember.) After writing a three hundred and twenty page backstory to justify why Old Man Henderson has such a ridiculous and varied list of skills (such as being fluent in certain foreign languages and being a championship ice skater), the player proceeded to carve his way through the DM's campaign and into tabletop gaming history. Special highlights of the game include Old Man Henderson obliterating an entire cult cell by crashing a fuel tanker truck into the center of its ritual, dropping a cult leader's yacht onto the penthouse of another cult leader (sparking off a Cultist Gang War,) and, in a grand finale, taking advantage of certain CoC rules/mythology and copious amounts of high explosives to... permanently kill Hastur itself.
 * Now we know the true identity of one of Lovecraft's recurring characters - The Terrible Old Man!
 * 4Chan has not only fallen in love with Henderson, but they even came up with "The Henderson Scale of Plot Derailment". One Henderson means that your actions have completely derailed the plot. TWO means you have screwed up so badly that the game itself is no longer salvageable, everything is dead, and the game has to be started over... just not in that universe.
 * 50 Copper and Ludi'drizz't.
 * There was an one-shot "guess what I think" side-quest with "thrown into unknown world" plot and random furry crossover setting trying to use Dungeons and Dragons (description doesn't lead to believe it was as much as d20 Future preview) as an impromptu substitute for Shadowrun. Loonie misadventures and massive elemental destruction ensue.
 * There was a fangirl's attempt to pass "Avatar with yaoi" as Dungeons and Dragons 4 campaign without telling the players beforehand. The party was supposed to See The Light and save elven tree-hugging Mary Suetopia from evil humans, but most chose to actually roleplay the proposed roles instead, leading to creation of what was nicknamed "The Elfslayer Chronicles".
 * The end result of the GM's plot getting between a Deathwatch kill team and loot.
 * The Plot would still be derailed, but it is easily fixed. If they run before the Avalanche, they get crushed while trying to lift off. If they go after the Avalanche, the enemies burn their way out of the bunkers and slaughter them. The next team will choose another way.

Western Animation

 * In the South Park episode "The Red Badge of Gayness," Cartman takes charge of the Confederate side of a Civil War reenactment and manages to get his side to win.
 * Kind of, he just got them hammered enough that they forgot all rules and regulations and were just obsessed with two things: epic level destruction and staying drunk.
 * One episode of Winnie the Pooh has Pooh narrate the story of the Three Little Pig(let)s that quickly descends into chaos when Pooh, being Pooh, keeps on slipping honey references in there and Tigger keeps on trying to "improve" the story. Rabbit makes a valiant effort to keep the story on track, but it all ends in a spectactular explosion of rain clouds and honey geysers. Literally.

Other
"Achmed Jr.: He's kinky too!
 * One argument in support of Death of the Author is the tendency for the creative process to escape the text's creator. In the course of writing them, characters can take on a life of their own and go Off the Rails.
 * In Jeff Dunham's comedy special "Controlled Chaos," Achmed goes epically off the rails when his leg falls off the platform. His Ho Yay with Marnel, the stage hand does not help.

Achmed Sr.: SHUT UP!"