Rubber Band History

Everything is right with the world! The birds are singing, the zeppelins are zoomin', and Adolf Hitler has finally defeated the last pockets of resistance in Australia.

...wait, what?!

It seems that the history we, the viewers on Earth 616, have grown familiar with is slightly... or hugely different. It can be an Alternate History where the Nazis won WWII, or even a complete reversal Mirror Universe where the characters we know and love have changed into Jerk Asses.

Rest assured though! Like a stretched rubber band, history may bend but will always spring back to its original form, and the more radical the change the nastier the Snap Back will be.

Our heroes in this strange and disturbing timeline will likewise undo it with Time Travel and reset it back into our history with a hearty "twang"! (Watch your fingers, and make sure you aim at the butterfly).

Sometimes, the resident Future Alternate Badass of said timeline will come back if the alternate timeline threatens to become dominant again. Don't expect them to stick around, though.

Comic Books

 * Neil Gaiman's Marvel 1602, in which the heroes and villains of the Marvel Comics Universe begin to appear 400 years early, qualifies, although it manages to avert the typical ending a bit:
 * Which is pretty much how this kind of thing tends to work with Marvel. They have to populate the multi-verse somehow!
 * Usually averted over at DC Comics, where it seems every little time-ripple gives Hawkman and Wonder Girl new origins.

Literature

 * K.A. Applegate's Animorphs did this a couple times. Elfangor's Secret opens with a normal day for our heroes: this great new game called Pong just came out, the extermination of the population of South America is going nicely, and even the slaves seem to be having a good time... wait, what?! (Since they don't have Ripple-Effect-Proof Memory until the Sufficiently Advanced Alien steps in, the first couple of lines on this page are pretty much exactly how it goes.)
 * And that's not even getting into the fact that one of the characters has been sent off for "reeducation" and there's someone else in that character's place.
 * Isaac Asimov's The End of Eternity. The title agency constantly changes the timelines, but in a few thousand years, the change inevitably smooths out..
 * In Dirk Gently's Holistic Detective Agency by Douglas Adams, Samuel Taylor Coleridge finished writing "Kubla Khan" and nobody's ever heard of Johann Sebastian Bach's music. It turns out that the music was.
 * Coleridge had to be interrupted (by a time traveler) because the last part of his poem would have started a chain of events leading to . The Bach thing, though, was just because the traveler liked the music he heard.
 * Variation: The Thursday Next books are set in an alternative history where, amongst other things, the novel Jane Eyre initially has a different ending from the one in 'our' world. However, due to the exploits of the heroine and the events of the final climax taking place within the novel's original manuscript, the ending gets changed to the ending it does have in our world - something which everyone greatly approves of, since in that history the novel's 'original' ending was widely accepted to be depressing and dramatically unsatisfying.
 * For added Mind Screw, the fifth book, First Amongst Sequels does the same thing with the Thursday Next books.
 * James P. Hogan's The Proteus Operation..
 * Ward Moore's novel Bring The Jubilee begins in a timeline where the Confederacy won the American Civil War; the main character goes back in time to observe Gettysburg and accidentally changes history to our version.
 * History in the Discworld is described as being rather stubborn, and hence, self-correcting. This is a large plot point in Mort, and later gets explained as the province of the History Monks and expanded in Thief of Time and Night Watch.
 * Mathematicians in Love by Rudy Rucker (though it's always obvious that the starting world isn't our own; e.g., the university across the bay from San Francisco with all the hippies is called Humelocke, not Berkeley).
 * The short story "Wikihistory" by Desmond Warzel reveals that history is vulnerable to the whims of, of all things, an amateur time-traveling society embroiled in a massive, history-changing Edit War.
 * Lawrence Watt-Evans's short story One-Shot has a guy go back in time to save Kennedy from being killed.
 * Philip Roth's "The Plot Against America" features a timeline in which Lindbergh becomes President in 1936, leading to a pro-Nazi America which oppresses Jews. However, by about 1946, world and US history alike are inexplicably back to the ones we know.

Live-Action TV
"Lister: It'll drive the conspiracy nuts crazy - they'll never work it out!"
 * The 4400 has an episode where Maya and other child 4400's were sent to the past and created the technology for non-polluting cars, moon bases, and biodegradable plastics. Despite things being better, Diana and Tom manage to convince the people in the future to undo their quite positive changes to reunite Maya and Diana, in return for a favor...
 * Andromeda: "The Unconquerable Man" was actually set in our universe at first, but when an additional scar was found on Rhade, we got a "Last Time In Another Universe".
 * Eureka's Season 1 Finale essentially pulls a Donnie Darko-style plot, but over the course of four years instead of a couple of weeks. Considering how much the fabric of the universe hated the fact that one person's life had been saved, we can only imagine how bad the snap-back would have been if they'd killed Hitler instead.
 * The Quantum Leap episode "Lee Harvey Oswald" leaps Sam into the title character, and Sam and Al have to decide whether the purpose of the leap is to shoot Kennedy, not shoot Kennedy, or something else entirely, since Oswald might not have been the assassin at all. It turns out that.
 * A few episodes were like that. The Marylin Monroe episode ended with Sam preventing her death from a drug overdose, keeping her alive long enough to make The Misfits.
 * In Stargate SG-1, after a hearty two-part alternate-history travel adventure, they come home to apparently their normal present. In a twist, however, now Jack's pond has fish in it when it's not supposed to. Jack declares the current universe is "close enough".
 * It's not "they come back to" so much as "the narrative goes back to". The two-parter began when the characters in the main timeline decided to go back in time to find a piece of valuable Applied Phlebotinum; historical records showed where it was in the past but by the present day it could have been anywhere in the galaxy. They succeeded, but at the cost of getting stuck back there and creating a very different alternate timeline Well, sort of very different. The alternate timeline's version of the heroes had to go back to restore the original timeline. All things considered, the series' true main characters only appeared in the first quarter of the two-part episode and the last five minutes.
 * Actually thinking about it, since seasons 1-8 are clearly in the 'no fish' timeline, the main characters of the show to that point died in Egypt and the last five minutes (and every episode or film in the 'verse since then) feature an entirely new, identical SG-1 as the protagonists.
 * One episode of Farscape has Crichton accidentally traveling to Earth in the 1980s, a result of which is his father now being slated to fly the Challenger's last mission. John and the crew of Moya eventually manage to get things right though, since as the alien "Einstein" had explained, history is literally like a rubber band and tends to snap back into place if enough things about the timeline are similar.
 * Subverted in another accidental time travel episode. After a long episode trying to help time right itself, they finally seem to have set things back on course. Only their presence in the timeline and the ensuing disruption it caused transformed a peaceful surrender into a horrible massacre.
 * A really nasty subversion occurred in Doctor Who, when he fixes something wrong in "The Long Game" and assumed the humans will sort everything out and get their development back on track. They don't.
 * Red Dwarf played this one for laughs in Tikka To Ride, involving the Oswald/Kennedy assassination. First time, the crew accidentally foils it and realizes they need to make it a stable time loop, so go through absurd lengths to try and get it back on track. After a few goes of it, they decide to skip to the future, only to find out that Kennedy has been impeached due to his numerous affairs, one of which with a woman that may have been a Soviet spy. They then convince the disgraced President to come with them and assassinate himself in order to avert the bad future.

Video Games

 * One of the Guilty Gear drama CDs takes place before the first game, but early on, one of the major characters from the games, Ky Kiske, gets killed. Cue a darker alternate universe, during which another character goes back in time to save Ky ...
 * The whole premise of Super Robot Wars Alpha Gaiden is this. The heroes get thrown into the distant future, while in the present their absence causes The End of the World as We Know It, meaning the world they land in is After the End. After they return to their time and prevent that disaster, the Bad Future continues to exist as an alternate timeline.
 * The Legacy of Kain games involve huge amounts of very confusing time travel, where various past events get changed by the main characters (whether deliberately or not). It is mentioned that after minor changes, history can shift a little bit to accommodate the change, and will then try to continue on approximately the same path. However, a warning is given that since history tries make changes along the path of least resistance, if the change is too great the people causing the change could be "expelled" from the timeline. What exactly this means is never explained, though since the hellish Eternal Prison level in Blood Omen 2 was said to be for people who had transgressed the laws of nature in some unspecified way, it is possible that that is the fate of those who meddle with the timestream too much.
 * Of course, for all the "defiance of fate" that was the theme of the series - up to the final (released) game being called "Legacy of Kain: Defiance", it turns out to have been Or, did it? The end of the game is a semi-cliffhanger, implying that now

Web Comics

 * Oddball variation: In Irregular Webcomic, the Indiana Jones parody strips feature Hitler as a Brain In a Jar - to circumvent the fact that the LEGO Group doesn't produce Hitler figures. This is later explained as the result of a change from yet another alternate history where Hitler died in the Reichstag fire. He was brought back in the jar by Adam Savage of the MythBusters as part of Chess with Death (specifically, a bet that Adam couldn't confirm the myth that Hitler's brain was saved in a jar... hey.)

Western Animation

 * Dog City: Baron goes back to the time the pilgrims purchased the new world from the natives and made a better offer: squeak toys. This created a Bad Future where he rules. Somehow, Ace and Eddie had Ripple-Effect-Proof Memory and, after visiting a timeline where Eddie ruled, went back to the past and made an even better offer: a technologically advanced (even for present time standards) fire hydrant the heroes took from the Eddie-ruled timeline.