The writer of You Got HaruhiRolled! went all out for the 81st chapter, written in commemoration of the story's one-year anniversary. In it, the craziness is ramped Up to Eleven and the situations are absurd even by Crack Fic standards. It's so nuts, the characters themselves are aware of it, especially after the writer self-inserts himself into the story and causes havoc. The chapter title is, you guessed it, "Off the Rails".
The Fanmake Blooper Series' main theme surrounds the idea that a Film Fic that's just a Transplanted Character Fic is doomed to get derailed simply because the characters have changed. And sometimes, the characters purposefully derail the story just to be entertained. A good example is the very first chapter of Sleeping Blooper, where during the scene where Maleficent (played by Queen Chrysalis) first appears, Van Helsing shoots her right as she was about to curse Kairi (playing the role of Princess Aurora). The rest of the fanfic is trying to make an entertaining story despite the fact that the main driving force of the story is destroyed.
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.
Spoonylampshades 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).
In The Cabin in the Woods, Marty and Dana escape the boundaries of the kill-zone by breaking into the underground facility through the Redneck Torture Zombies' grave.
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'.
Un Lun Dun seems like your average "Chosen One goes to another world and goes on a quest that is also a Coming-of-Age Story in between all the Fetch Quests" story. Then the Chosen One gets bonked on the head, and it's up to her friend (Who was, according to the prophecy, the funny sidekick) to go on the long, epic, Fetch Quest-filled journey. Except, after the first one, she decides (Correctly) 'I don't have time for this shit,' gets the Un-Gun, and becomes the Unchosen One.
ThisRobot Wars fight. A 4-way free-for-all begins with House Robot Shunt getting flipped onto its side in the first five seconds of the match. Hilarity Ensues from there. Outrageous stuff from the fight includes the Refbot falling into the Pit Of Doom, the OTHER House Robot getting caught in a 4-on-1, and a washing machine landing in the middle of the arena. Yes, that last one is true. The result is eventually decided when two robots suicide into the pit, 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.
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 photonic aliens mistake it for reality and declare war on Chaotica.
Likewise when Seven uses the Leonardo da Vinci holoprogram for a little time to herself.
Janeway: Master da Vinci doesn't like visitors after midnight. Seven: He protested. I deactivated him.
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 simply attempts to pastiche elements from the novels, and (let's repeat) Data had read them all. The next time they try a holo-novel, Geordi accidentally asks the computer to create "an adversary capable of defeating Data" (not Holmes). 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 punched out Lancelot when he came on to her in a King Arthur game where she was playing Queen Guinevere. She was supposed to be 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.
Q: Picard never hit me! Sisko: I'm not Picard.
Holodecks and holosuites, however, did seem to have some capacity to adapt to such sudden shifts. For instance, when Garak intruded on Julian Bashir's program, the holographic characters had no problem working with him once he was introduced as the hero's friend, and when Bashir pulled his Face-Heel Turn stunt and pushed the button on the villain's machine that destroyed the world, the villain acted rather puzzled for a moment and admitted that somehow he hadn't really expected his plan to work. Then, since knocking off the hero was programmed into his personality, he raised his gun on Bashir again, figuring that maybe he'd better kill him anyway just to be on the safe side.
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:
"Well, that's that sketch knackered then, isn't it?"
Michael Palin did this himself during performances of the infamous " Dead Parrot Sketch", in an attempt to throw John Cleese 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 Cleese responds, "Right; I'll have that one then."
Another time Palin disrupted the sketch was when he answered (to the same question) "Well, he mutters a little" which caused Cleese to break down with laughter and, once he could continue, ask the audience where they had gotten up to so they could carry on.
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. Wannaknowwhy?
As of 2010, the show is supposed to go until 10:00, and it's still overtime.
Frequently happens during the Sound effects games, do to the people's selected utter ineptitude of making sound effects. For example, the story of Noah ended when Noah and his wife getting watching the Arch... err... log floating away, leaving them to die to the flood.
It happened during a game of Song Styles, when Wayne was singing to audience member Howard in the style of the Village People (specifically spoofing "YMCA"). He'd already messed up by misspelling Howard's name as "H-O-R-W-A-R-D", or "Horward", but it got nuts when keyboardist Laura Hall accidentally increased the song's tempo.
Wayne: (singing) Howard, can you last? Howard, how'd this song get so damn fast? Oh, Howard...
In the MythBustersMacGyver 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. As the solution was both effective and in the spirit of the challenge, it was deemed successful.
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. He does, however, attempt to justify it; while Adam had gone over budget, the finished product was not.
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.
Richie: "You know my great watch gag? Well I've forgotten to put it on."
Eddie: "Well, that's shagged that, then!"
In an episode of Top Gear about track day cars, Richard and Jeremy mention how James cheated during a game of Monopoly by staging a robbery of the bank. May attempted to defended himself by saying it "made (the game) more authentic".
In the Amy's Baking Company episode of Kitchen Nightmares, the entire episode goes off the rails when a stagehand has to step out to break up a fight between co-owner Samy and a customer. The episode, then, proceeds to jump the rails and disappear into a forest as Gordon Ramsay watches as both Amy and Samy fight him tooth and nail over everything, culminating in Amy firing a waitress because she asked a simple question.
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 aSingle 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.
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".
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 had 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 (thus 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.
Whoa. 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.
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.
In a 4th Edition D&D played via IRC chat, a lesbian Bard with an overly-rape-filled backstoryand an intense hatred for men refuses to help or even speak to male players in the party. She persuades the DM to include a plot of her design into the game, which involves the group saving a bunch of refugees that is mostly comprised of women. At a ceremony celebrating their victory, the Bard announces that she has created two rituals that will kill all men and create a utopian, war-less society of women and hermaphrodites, respectively. Her Diplomacy roll succeeds...but another player runs in with a Howling Strike, and over the course of several turns hacks her to unconsciousness. Then a female Fighter steps in and delivers the killing blow, saying, "Some of us like MEN attached to dicks,you selfish cunt."
Happens fairly often in Legend of the Five Rings, since the storyline is based on tournament results. Sometimes, when players go entirely against the grain, entire storylines can be derailed; an arc's Big Bad underwent a Heel-Face Turn because a mass movement of Dragon Clan players flatly refused to use corrupted decks, despite the Dragon Clan cards of that era being designed to support a corruption-heavy playstyle.
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.
At about two thirds of Into the Woods, the characters find themselves forced to sacrifice a man to a giantess. The narrator laments their cruel fate. They all promptly look over at the narrator and decide to sacrifice him.
The Elder Scrolls III: 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. Unless you kill Yagrum Bagan, who is necessary to the back-path.
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.
Due to the way of how many you actually "Win" Morrowind, there's only three TRUE ways to break the game. As long as you don't misplace two plot artifacts which are not tied to quests but rather to boss loots, you can beat the game even without the third complicated quest artifact (Which is the reward for the "normal" questline to begin with.) allowing you to skip 99% of the game if your strong enough to use them without dying instantly. The other is save in the final area without said plot artifacts. The last is somehow being able to destroy the Plotline "Boss" Actually the Heart of the World which cannot fight back but can't "die" except to the plotline Artifacts normally. which is possible but difficult without exploits.
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 smashing you into the elevator shaft and dropping you into Old Aperture; third, when you escape Wheatley's Death Trap in "The Part Where..."
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 the Citadel. 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 -
The developers did anticipate a couple of these skips. If you already know where your father is when talking to Three Dog (or smooth-talk him into telling you before his errand), 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 Yes Man. Unfortunately, it's impossible to go off this rail since Yes Man is more or less immortal, and doesn't even care if you open fire on him repeatedly since his programming will just be transferred to another securitron if the one he's in is destroyed.
If you play the NCR route, it's possible to complete the game without ever confronting Benny or getting the Platinum Chip.
In the Honest Hearts add-on, you can go off the rails of helping the Zionites by killing people integral to the plot or getting caught stealing. If you do, the quests to help Zion will immediately fail and a new quest, "Chaos in Zion" will start - it consists of you getting one of the maps Daniel drew so that you can find your way back to the Mojave Wasteland. (However, the Sorrows, Dead Horses, and New Cannanites all now want you dead for some reason.)
The Nameless Mod includes a few ways for the player to go off the rails, including having one of the endings dependent on going off the rails several times.
Specifically, Trestkon as the PC must complete 3 out of 5 possible actions that are considered "impossible" in-game (such as getting access to Despot's apartment when your character doesn't have the in-game knowledge of how to do so). Completing these actions leads the Narcissus Entity (the in-game AI director of, well...everything) to Break The Fourth Wall, leading to an opportunity for the player to take Narcissus' place a small time later.
Additionally, should Trestkon kill Scara B. King in person rather than banning him at the end of the game, Narcissus will kill you for breaking the game.
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 herself and get annoyed with you for refusing orders) or do the job yourself — or waste Navarre (causing Alex Jacobson to freak out) and Lebedev will complete the explanation of what's going on.
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 betray the side he's working for and murder his partner 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 UNATCO betrays you. 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 Human World bill in Disgaea 1, and you'll get an opportunity go invade Earth instead of moving on to Celestia. This leads to a couple mildy difficult encounters, followed by a final showdown where General Carter turns into a Prism Ranger, you beat the crap out of him, and then take over the earth.
"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.
Replaying the stage where you fight the ghost of 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 & the World Eaters, this leads to a fight with Asagi, who blows up the planet after beating her (it's even lampshaded by Gig). The Demon Path is something of a campaign based solely around this, since it begins with Revya accepting Gig's Deal with the Devil and killing Layna.
An in-universe example of sorts takes place in The Reconstruction, but not by the main characters. Throughout most of the game, the Watchers seem like the main masters of the plot, with some kind of grand scheme that your guild has been working towards. But then suddenly, the Big Bad derails everything by killing them and taking over the world.
This entertaining video shows how a player can use hacks and cheats to send the opening of Skyrim flying off the rails at insane speeds. Some highlights include two people who are scripted to die surviving, an army of Alduin clones, giant chickens, and the player using hacks to kill an entire regiment of guards and critically wounding one of the Alduins before being blown to bits but a blast of fire.
Invoked in Super Paper Mario. In Sammer's Kingdom, the party is told that it must fight 100 Sammer Guys in a row. The format of the game so far has been set up to suggest that the player will fight 25 Sammer Guys in each of four levels, before receiving the Pure Heart at the end. The player doesn't even finish the first level when Count Bleck and his minions arrive to destroy that world. The party survives the destruction and returns to the world's ruins, only to be sent to the next world by Dimentio, and thus plays the seventh world early.
Little Bustersis set mainly in a world of Kyousuke's creation. While it normally functions well enough, there are two examples of Riki inadvertently setting it off the rails: firstly, he ends up falling for Kurugaya and in doing so causes the world to break down because this was completely unexpected and so unaccounted for in the world's structure. Secondly, and much more disastrously, there was Kyousuke's plan to send Rin off to another school in order to get her used to the real world and toughen her up. It ends up being harder on her than he expected, and more importantly, Riki does not go along with it. In the end, he runs away with her, and ultimately ends up losing her completely.
The Stanley Parable. While there is a story that comes from doing exactly what the narrator tells you to do, (which, ironically, is about a man who frees himself from a mind-controlling machine) the vast majority of the game's content, multiple endings and entertainment value comes from going repeatedly off the rails. Depending on when and what you do, the narrator/GM will try to cajole, threaten or manipulate the player into returning to the main story path, try to create new story narratives, mock the player character, mock the player, encourage the player to strike out randomly to see what you find, break down in despair at your unwillingness to play ball, attempt to destroy the game world, plead with you to prevent you from destroying the game world, and generally get more erratic the further you go.
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.
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 & Burrows (a game where all the characters are normal, mundane rabbits).
Darths & 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.
The offscreen campaign where Jim was the GM is a partial example. Nothing was derailed in terms of the plot, but he intended the campaign to be very serious and dramatic while the players took it (and loved it) to be hilarious. This makes a lot of sense since his campaign was Airplane!!
A couple of the "alternate" strips go Off the Rails:
In a non-canon strip, Jim uses Summon Bigger Fish and doesn't take it back thus killing the queen and her retinue.
An out-of-universe example is the killing of Greedo senior, thus making the "Greedo" from Episode IV "Han Solo" and "Han Solo" "Greedo". This is not unusual for the comic due to the Random Number God and the players doing the unexpected. Other examples usually have to do with killing characters the GM doesn't want them to (i.e. General Grievous), killing characters they weren't supposed to (Darth Maul/Zam Wesell), killing character's before they were supposed to (Jango Fett), not taking the obvious hints to go to someplace or do something (which inadvertently sends Boba Fett to want revenge and Naboo being defeated), etc. Several times the GM made very detailed maps of an area just to have the players go through the center of the Earth or book someplace weird.
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 Legolas kills Gollum early on. And later on they even get to kill Gríma Wormtongue and Saruman.
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 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 session afterward went Off the Rails before the game even started. 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. It got further Off the Rails when due to circumstane none of the post-scratch kids prototyped their sprites before entering the Medium, which causes the Battlefield to never fully form and the game to be nearly completely Unwinnable.
And then Caliborn manages to take the cake by attempting to play all by himself, which turns the Medium into a desolate dead place. Caliborn isn't very worried since Hussie informed him that it was like playing in the highest difficulty setting.
Aranea claims that Caliborn's species was never meant to play Sburb at all. The game went off the rails the moment Caliborn & Calliope entered the game.
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.
We also see such gems as:
Brian trying to take out a nemesis by throwing a sack containing 47 12-ounce bottles of nitroglycerine. The result is mistaken in-universe for a meteor strike.
Sarah gets a chance to run the top-of-the-line module Adventure To Castle Lonely, only for the players to refuse to even go to the castle and run off chasing squirrels.
Brian shooting Bob's new character for no discernible reason.
The party defeating a dungeon by sweeping all the traps with animals.
At one point Frank turned this against them by setting up a campaign where successful power-gaming required them to spend a large amount of time role-playing. When they realized he had planned them going off the rails from the start, they went further off the rails by deciding to Kill 'em All.
The very first thing that happens in Erfworld. One faction finds one more jewel than they were planned too, which lets them buy an extra unit, which turns a critical battle, which sets the actual plot in motion.
At the start of the second game session of Larp Trek, before Geordi (the GM) can even open his mouth, Picard and Wesley get a murder mystery going.
Picard: Geordi, were the holodeck's usual safety protocols disabled? Geordi: Don't look at me, Captain. I wasn't even on this train when it left the station.
Early on in One Piece: Grand Line 3.5, the players work to derail the campaign as soon as they hear there are pirates in it, mostly so that they can be pirates themselves. These are the players that will eventually control Luffy and Zoro.
Later, the GM does it to himself. When he rolls a Critical Failure for the arc boss's attack on an NPC, it grants that NPC an immediate Attack of Opportunity, at which point the GM throws three natural twenties in a row, an Instant-Win Condition. The end result: Sanji.
Spoony's story about Vegan Steve and the Deck of Many Things is a living testament to this: Spoony had based his campaign around cursing the player characters to turn into mindless animals unless they find a Genie within a week and wish to be cured. However, when they finally summon the spirit and it offers them a wish, Vegan Steve shouts: "I wish for a Deck of Many Things!" After all the other players try to murder his character in retribution, he runs off, pulling cards off the deck at random.
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.
Then there is his Shadow Run story, where his characters botch a stealth roll during a routine B&E in a low security museum, panic, then start barricading the place, having shoot-outs with the guards, taking them hostage when the cops arrive (along with a couple of janitors), and then blowing hostages away and tossing the bodies out the door. They eventually escape through the sewers after wiring the museum with enough explosives to level a city block and murdering the remaining hostages...only to run into a waiting Cyberpsycho squad placed there by a thoroughly horrified and pissed-off Spoony.
In the South Park episode "The Red Badge of Gayness," Cartman takes charge of the Confederate side of a Civil War reenactment. The result is them getting roaring drunk, going on a rampage and winning.
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.
There was an episode of U.S. Acres where Orson tried to read "Rumplestiltskin" to Booker and Sheldon. The boys keep asking Orson to change the characters into things like ninjas or monsters, but Orson puts a stop to that for the most part. Then Wade (who played the miller's daughter) butted in and had the daughter be changed to a son, and as a result, the price to be paid became the son's VCR. Things really got crazy when the miller's son was about to guess Rumplestiltskin's name because Roy (a Super Hero-style Rumplestiltskin) tried to alter the ending in his character's favor, much to the protest of Wade and Orson:
Roy: But before the duck son could say the name, a hurricane came up!
Orson: A, a hurricane?
Roy: Yes, a hurricane that blew the duck away so he couldn't take his VCR back.
Wade: Uno momento!
Wade: Then, a spaceship came by, and it rescued the handsome duck, and flew him back to reclaim his VCR!
Orson: Guys, stop this.
Roy: But the rooster was determined to get it back with the aid of his, uh, trained dinosaurs!
Orson: Trained dinosaurs? Where did the trained dinosaurs come from?
Roy: Same place all those ninjas came from.
Wade: But then the Third Marine Division landed, with their Anti-Trained-Dinosaur Squadron!
Roy: But the Mole People were too smart for the Marines!
(a few minutes later)
Wade: —Then eighty-three monsters take the VCR back!
Roy: Then eighty-four monsters and a giant moth grab it back from the duck!