Set Right What Once Went Wrong

""Theorizing that one could time travel within his own lifetime, Doctor Sam Beckett stepped into the Quantum Leap accelerator -- and vanished. He awoke to find himself trapped in the past, facing mirror images that were not his own, and driven by an unknown force to change history for the better. His only guide on this journey is Al, an observer from his own time, who appears in the form of a hologram that only Sam can see and hear. And so Doctor Beckett finds himself leaping from life to life, striving to put right what once went wrong and hoping each time that his next leap... will be the leap home.""

- Opening, Quantum Leap

The character receives foreknowledge of what will happen (or, if Time Travel is involved, Ripple-Effect-Proof Memory will allow them to remember what happened "the first time around") and has to correct it.

Constitutes the plot of nearly every episode of Quantum Leap (from which this title was taken), Early Edition, Seven Days, and Tru Calling, as well as a majority of episodes of The Dead Zone, and numerous individual episodes of other shows. Can form the Arc of a whole series, as in Heroes.

Distinguished from Groundhog Day Loop by:
 * 1) The character's knowledge of what needs to be corrected prior to the first time through, and
 * 2) Usually only one attempt to correct it is necessary or in fact possible.

Combinations of Groundhog Day Loop and Set Right What Once Went Wrong are possible, however, and have been used on occasion: see for example "The Siege" on The Dead Zone, the Tru Calling episode "The Longest Day", Early Edition ' s "Run, Gary, Run." In fact, this combination is the entire premise of Day Break.

Sometimes, trying to Set Right What Once Went Wrong is what sets everything wrong in the first place, resulting in a Stable Time Loop and Two Rights Make a Wrong. Succeeding would create a Temporal Paradox (i.e. if you do manage to set right what was wrong, you would have no reason to travel back in time in the first place, which means the wrong-ness would still be there, so you'd travel back in time, etc.) When the purpose of the time travel is to save a person (but not alter the timeline) by pulling the person out of time, it's a Time Travel Escape.

Often the adventurer has to travel to fix things, combining this premise with Adventure Towns. This premise has also been applied to literature rather than time, with characters trapped in a Portal Book interfering with the book's original plot and being forced to set things back on track to resolve "the right way."

Contrast Make Wrong What Once Went Right, where the time traveler acts for either selfish purposes or because they're living on Crazy Street.

Note: World War II did not go wrong. Traveling there will only make it worse.

Anime and Manga

 * The plot of Higurashi no Naku Koro ni once the protagonists realize that they've  of murder, insanity and betrayal.
 * Steins;Gate runs on this trope. The protagonist Okabe voluntarily relives the same couple of hours over and over  Then, upon realizing   The series ends with a truly Mind Screwy plan
 * Generator Gawl seems to fall into this category, seeing how the only reason Auge was able to take over was because Gawl, Koji, and Ryu went back in time to stop them. In the end Ryu was the one who created the include cells and gave Auge the ability to take over, which is what caused them to go back in the first place. Ouch, I think my brain just exploded.
 * An attempt at this is the driving force behind the Myth Arc of Rave Master. The series inverts the trope because changing history back to the way it was is the bad guys' plan, as the original timeline's world was utterly destroyed save one survivor, who was able to change history to create the Rave world. On top of the Eldritch Clock Roach out to undo the paradox involved, most of the late-story baddies want to see the "false" world destroyed.
 * The premise of Flint the Time Detective. The Time Shifters got scattered throughout history, changing the way certain historical events played out, and the Time Detectives have to captured them and put the past back the way it was.
 * The entire final arc of Full Metal Panic! is about this, as it's Leonard's motive behind all the trouble he causes. It's why he kidnaps Kaname, why Kalinin, why . They intend to go back in time to prevent so that the world would be more peaceful. Only the Whispereds will know that anything has changed.
 * from Puella Magi Madoka Magica leaps time to save from becoming a, or more commonly known as a  that may transform in the future into a ..
 * One of the arcs in Kurohime involves two of the titled character's foes (Kurohime considered a bad guy in that world) going back in time to try and kill her, for personal reason (revenge being the main motive, but also to keep the father of one of them being killed by her.)
 * Amakusa 1637 is built around this trope. Six schoolers from modern Nagasaki end up thrown in the Nagasaki of 1637, few before the failed Japanese Christian rebellion of Shiro Amakusa; they decide to pull this trope to avert such tragedy.

Comic Books

 * Exiles was supposedly pitched as Quantum Leap or Sliders with superheroes.
 * Booster Gold does this quite a bit as the secret protector of the time line. It's when he has to set wrong what once went right or keep wrong what once went wrong that things get really morally complicated for him.
 * In one issue of Paperinik New Adventures, the incident to be stopped in question is a major disaster in present-day Duckburg that would destroy a large part of the city and everyone there, while the one trying to stop it is a time traveller from OUR future. Obviously, when Donald Duck's superhero alter ego learns of this, he does everything in his power to stop it, thus getting in trouble with the Time Police.
 * In Marvel's Civil War storyline, the entire event was kicked off when Namorita, a member of the New Warriors, fought a villain named Nitro whose ability was to explode. Said explosion killed hundreds, including Namorita herself. Because of this, Namorita's name was posthumously slandered with the rest of the New Warriors, much to the chagrin of her ex-lover, Richard Ryder aka Nova, even though they'd been broken up for years at that point. In his eponymous series, Nova is plucked out of the timestream along with a Namorita who is obviously from an era not only before the Civil War incident, but while she and Ryder were still lovers. Later, when the cosmic forces that threw them together start to send them back where they belong, Nova (being a Paragon-type character), refuses to let Namorita return to her own time (where she'll be doomed to repeat the same fate) and brings her to the present instead...consequences be damned.
 * In an issue of Marvel Two-in-One, the Thing goes back in time to cure his past self of being an orange-skinned monster and change his own life, but only succeeds in creating an alternate timeline where a now-human Ben Grimm quits the Fantastic Four and is replaced by Spider-Man. This becomes Make Wrong What Once Went Right in a follow-up story, when it is revealed that the absence of the Thing on the FF results in Galactus succeeding in his initial attempt to feed on the Earth, leaving the remnants of humanity with a Crapsack World low in vital resources.

Fan Works

 * In the Warhammer 40,000 Fanfic/Play by post story Abaddon Quest, there's a rather amusing Inversion, the eponymous Chaos Lord and his flunkies travel back in time to kill the God-Emperor as a baby, which is to say they travel back to Set Wrong What Once Went Right. Considering /tg/'s Opinion of Abaddon, Failure Is the Only Option. As is Hilarity.
 * In Heta Oni,
 * Neon Genesis Evangelion
 * Subverted in Evangelion RE-TAKE.
 * Played straight in Going Another Way, where
 * The Pony POV Series Recursive Fanfiction Fading Futures has Twilight Tragedy manage to break free of Discord's control in the Epilogue timeline and seek to change the past so that Discord never won in the first place. She manages to do so, but as a result, the timeline she inhabits no longer exists and everything in it are "reborn" into their main timeline counterparts.

Film

 * The Girl Who Leapt Through Time involves a girl who learns she has time-traveling powers, but each jump makes things worse. She has to stop herself from screwing everything up over and over.
 * In Triangle this is what Jess tries to do after she realized she's in a Groundhog Day Loop.
 * Most of the Back to The Future sequels: the second one begins with Doc taking Marty to the future to stop his son from getting arrested, and then having to go into the past to stop teenage Biff from using a Timeline-Altering MacGuffin to become evil and rich. The third movie has Marty go back to 1885 to stop Doc from getting shot by Buford Tannen. The main problem in the first movie, however, is Marty's fault to begin with. However, Marty's eventual solution to this problem has the unexpected bonus of his father being more confident and assertive over Biff in 1985, leading to this trope in a roundabout way.
 * Cyborg 2087. In the far future, a mind-control invention has been abused to create a police state controlled by cyborgs. Garth, a good guy cyborg, travels back to 1966 to convince the invention's creator to keep it secret and thus change the future.
 * The two time travelers in each of the Terminator films are each trying to set right the wrong the other one caused.
 * The film Frequency is about a man who can communicate with his dead father through a family ham radio thanks to an Aurora Borealis that appeared in the same timespan between 1969 and current-day 1999. He uses this communication to save his father from his impending death in a warehouse fire, but that sets off a chain of events that lead to his mother's death, so the two work together to fix that, but then... et al.
 * The plot of the Stargate SG-1 movie Stargate: Continuum centers around the main cast being the only people to know that the timeline has been changed and trying to convince others to let them change things back. The trope is notably deconstructed when SG-1 gets a What the Hell, Hero? speech upon suggesting time travel; the issue is raised that this trope requires an Omniscient Morality License to work and that to assume you can go around Setting Right What Once Went Wrong is an act of staggering arrogance as it necessitates changing the lives of millions... of course it always Gets Worse and they're allowed to do it in the end.
 * Viciously subverted by the film The Butterfly Effect, in which every time the main character goes back in time to fix something the titular concept conspires to make things worse for everyone. This occurs repeatedly with all kinds of nastiness happening along the way, culminating in an inevitable Downer Ending the exact nature of which depends whether you're watching the theatrical release or the director's cut.
 * The basic premise of Time Cop, to fix what the baddies are doing in the past and avoid the aforementioned butterfly effect.
 * In The Time Machine (2002) Alexander Hartdegen's original motive for inventing his time machine is to prevent his fiancee from dying in the park. However, the movie subverts this trope, as his every effort to save her causes her to die anyway from another cause. It is explained later that were it not for that tragic event, he would never have finished his invention, which would have precluded him going back and saving her.
 * The heroine of the underrated Retroactive finds herself timelooped due to close proximity to an underground time travel experiment. She is witness to a murder, and tries to use the shortish (20-minute?) loop to alter the outcome. Results vary.
 * In OOO, Den-O, All Riders: Let's Go Kamen Riders, history was accidentally altered thanks to a Cell Medal being left in the past during a fight. This resulted in Shocker defeating the Kamen Riders and conquering the Earth. So the plot of the movie revolves around going back in time to set it right.
 * Subverted in the Final Destination series. One character's foreknowledge allows him or her and a group of friends to escape some kind of fatal accident. The rest of each movie is about death trying to fix this event that "went wrong".
 * A core concept of Battle for the Planet of the Apes, with Caesar and co trying to stop the Earthshattering Kaboom of 'Beneath The Planet Of The Apes' from ever occuring.
 * Brazilian film O Homem do Futuro (The Man from the Future) has a guy accidentally going back to the prom that ruined his life, and guiding his past self so things go right. Unfortunadely it leads to future where he's a rich jerk and the love of his life hates him, so he again goes back to make sure things go back the way they originally happened (including passing the details on how his date should humiliate him).
 * In the film Split Infinity, financially-minded teenager Amelia Jean falls from a barn loft and wakes up as her own late (by her time) great aunt for whom she was named. She tries to prevent her brother/grandfather from losing everything to the impending Black Tuesday. She succeeds only in learning a lesson about what's really important, and setting things in motion that would cause them to be the way they would be by her time. (And quite possibly confusing her great aunt when she returned to her own time...)
 * Primer. The plot involves

Literature

 * Teresa Edgerton's Celydonn books, specifically The Grail and the Ring, have an interesting take on this. Strictly speaking, Time Travel is not possible. However, Functional Magic allows one to travel to the Inner Celydonn, to a shadow of the past, where one can see what really happened if one doesn't try to derail events. This quasi-Time Travel is used to find out What Once Went Wrong, so that it can be Set Right in the present, thus avoiding any Temporal Paradoxes.
 * The The Caretaker Trilogy Trilogy focuses on people from a future where the world's ecosystem has been ruined coming back to the present: the "Turning Point", or the point at which it was theorized to still be possible to reverse the damage done. Their foes, who actually like the future as it is, also come back, with the aim of speeding up the damage, and ensuring their own victory.
 * A Christmas Carol has this with the Ghost of Christmas Future warning of the deaths of both Tiny Tim and Scrooge, which Scrooge then fixes thanks to Scare'Em Straight.
 * In Mergers by Steven L. Layne, the titular Mergers must go back in time to make sure that a man named Michael Quinn dies as a young boy.The reason why is that  Somewhat different from the usual situation, in that usually it is the opposite(them saving the person).
 * Throughout the early Nightside series, John Taylor
 * The protagonist of Jack Chalker's Downtiming the Night Side is forced to choose sides in a temporal war. Naturally, both sides claim to be battling those who would Make Wrong What Once Went Right in order to Set Right What Once Went Wrong.
 * Poul Anderson's The Corridors of Time has essentially the same plot, with added saga and mythology.
 * Elizabeth Haydon's Symphony of Ages is this all over.
 * Thursday Next's father's intent throughout The Eyre Affair. Whatever else they feel it important to talk about, her father always asks Thursday about the outcome of some major battle. His normal response is to swear and vanish (presumably to the battle he asked about), but the whole thing is lampshaded when he asks about one he asked about earlier in the book, and Thursday exasperatedly tells him that the answer hasn't changed since he last asked, but the actual answer she gives is different.
 * This is one of the main plots in Roger Zelazny's Roadmarks, which has a road that travels from one end of time to another with off-ramps into various alternate histories. If an off-ramp doesn't get used, it eventually vanishes. The main protagonist, Red Dorakeen keeps trying to run modern firearms to the Battle of Marathon to change the outcome, thus re-creating an off-ramp that will allow him to find his lost home. At one point he sees Hitler, traveling in a VW Bug, “trying to find the place where he won.”
 * Chronicles of Chrestomanci
 * Diana Wynne Jones likes this trope. In Witch Week a cataclysmic event has caused an alternate universe to split off, which is identical to ours in every way except that magic exists and witches are persecuted and burned. In order to merge the universes, the characters have to work out what the cataclysm was, and use their combined magic to change history so the universes will never have split in the first place. As a side-effect, various characters' parents haven't been executed or imprisoned in the new universe.
 * In A Tale of Time City there's a lot of time travelling, but you can only change the past in an "unstable era". The characters travel three times to the same station platform in 1939 in an attempt to change the results of events, but the results are unpredictable and they never manage to improve the situation. Meanwhile, the changes they cause create greater instability each time...
 * Isaac Asimov's End of Eternity is based on this trope. A group known as Eternity exists outside of time, constantly intervening to maintain peace and order. However,
 * The capacity for doing this appears in the later books of Peter F. Hamilton's Void Trilogy. It turns out that "The Void", a Pocket Dimension accessible via a giant singularity has a "reset to time X" function built in, accessible to anyone that knows it's there; as is traditional everyone but the resetter forgets the original timeline. (The downside is that the act of rewinding an entire dimension needs lots of energy, and the Void obtains that by expanding and eating a bit more of the surrounding "real" galaxy's mass. This isn't very popular in the real galaxy.)
 * Attempted in the novel Time and Again, sequel to From Time to Time (unrelated to the Naruto Fanfic of the same name). In this universe, time travel to the past is possible for a select few with the proper training. The main character in Time and Again goes back to 1912 in an attempt to prevent World War 1. He knows that there was a man who went to Europe to negotiate an agreement that could have prevented the war, but the agreement never made it back to the US. He later finds out that this was because the man and agreement went down with the Titanic. His next attempt is to prevent the ship from sinking. Another time agent alters the ship's course the tiniest bit, so that the ship will miss the iceberg by a few inches.
 * The premise of R. J. Rummel's Never Again series of novels is the main characters traveling back to 1906 to undo all the atrocities of the Twentieth Century and to spread democracy throughout the world. It gets a lot more complicated than it seems at first.
 * Subverted in Pendragon where Bobby thinks that he setting right what once went wrong by stopping the Hindenberg's destruction, but if he had stopped it, he would have doomed the entire world.

Live-Action TV

 * The Trope Namer is Quantum Leap, whose entire plot is a series of these.
 * Tru Calling: Tru does this in almost every episode. A number of twists and variations of the trope are also used.
 * This was also the plot for the entire Voyagers! series where Phineas and Jeffrey would travel through time to "give history a little nudge".
 * Appears to be the premise of the lamentably late NBC series Journeyman.
 * One episode revolves around him trying to undo something he did by accidentally leaving his digital camera in the 70s. He returns home to find that computer technology is decades ahead of what it was (holographic screens and video-newspapers are commonplace), but his son was never born (he was delayed at work due to a computer error), replaced instead by a daughter who was conceived a few days later. Despite his wife's objections, he goes back and fixes it.
 * Odyssey 5, where a Five-Man Band witnesses the destruction of Earth from a space shuttle and are sent back in time five years by Sufficiently Advanced Aliens to prevent it. Although they promise not to change events, each of them can't resist meddling with their past to make it better. For instance one woman who knows her son will die of cancer starts giving him a potentially dangerous preventative drug—her husband, convinced she's going insane, cuts off her access to the boy. Another character bets on a football game—the size of his bet leads to other people betting on the outcome, starting rumors that adversely affect the course of the game. Worse, the group have consider the possibility that their own actions might advance in time, or even cause, the destruction of Earth.
 * Seven Days is entirely about this trope: a time machine allows a government agent to go seven days back in time in order to prevent the catastrophe of the week from taking place.
 * The main plot of the first three seasons of Heroes, though this is more of a case of Set Right What Will Go Wrong. Name dropped by Hiro in Season 5's "PassFail" during his all-in-his-coma-mind-trial, and Mental!Adam/Kensei rightfully points out that he's simply reciting the opening to Quantum Leap.
 * Another example of this is the CBC drama, Being Erica, where the majority of episodes were centred around her travelling back to a point in her past where she tries to put right something, she believes, went wrong in her life. Normally it would turn out that actually she needed to learn a lesson from that event and her changes wouldn't help her life that much.
 * Angel{{'}]s Crossover with Buffy the Vampire Slayer, "I Will Remember You."

Music

 * Ludo's rock opera Broken Bride follows an obsessed scientist, who invents a time machine so he can go back and stop his wife from dying in a car accident.

Video Games

 * An elementary tactic in Achron. Occurs often in multiplayer games as a response to another player screwing with your past.
 * Basically the whole premise of Daikatana, although the main characters spend so much time screwing around in the mythic past that one could be forgiven for thinking it was otherwise.
 * The plot of Marathon Infinity in the round-about way.
 * This is the premise of the fan-made Game Mod Marathon: Eternal. Earth is devastated by an interstellar war, and the hero is sent back in time to ensure that Humanity wins. Avoids a Temporal Paradox because the Lost Technology doing the time traveling can also jump between different dimensions - the plan is to create an alternate timeline where Earth isn't destroyed and transport the refugees from the original Earth there.
 * We learn in the end of Arc the Lad 2 that
 * Final Fantasy
 * The whole point of the Wings of the Goddess expansion in Final Fantasy XI.
 * The point of Final Fantasy XIII-2 is to fix the timeline and help everyone find happiness while averting future disaster.
 * In Dark Fall 2: Lights Out, Parker stumbles into a time portal while investigating the disappearance of some lighthouse keepers, and discovers . Likewise, while Darkfall: The Journal.
 * The overarching plot of the popular Half-Life Timeline mod trilogy. Scientists at Black Mesa discovered time travel as a corollary to the dimensional portal technology they were working on... and gave it to the Nazis. Now Gordon must travel to the ends of time and even to parallel Earths to Set Right What Once Went Wrong and stop the Nazi timeship fleet,.
 * Implied in-game and inferred by fans in regards to The Legend of Zelda: Ocarina of Time, and also one of the cornerstones of the infamous Split-Timeline Theory. The whole game deals with Link's efforts kick Ganondorf off the usurped throne of Hyrule (which Link was sort of responsible for in the first place), which he succeeds at with the help of Zelda and the sages. Then Zelda sends Link back to before all that happened so Link can experience the childhood he was robbed off. Link therefore uses this opportunity to warn Zelda and everyone else of how Ganondorf was planning to steal the Triforce, which leads to Ganondorf being captured and executed. However, . So things were set right, but they ended up going wrong in a different way.
 * In the Interactive Fiction game Jigsaw, the antagonist is trying to set right what once went wrong (preventing the assassination of Archduke Franz Ferdinand, for example), while the player character must try to keep history on track. (At least, that's how it starts; then it gets a bit more complicated.)
 * Radiant Historia is about a soldier who is given a book called the White Chronicle, allowing him to travel back to certain points in time on his journey to help guide the world to its "correct" history (i.e. one that doesn't lead to its destruction through constantly-expanding desertification). Invoking this trope is required to complete the game. Many other temporal tropes apply at various points in the game, but this trope pops up beautifully in a simple sidequest: a woman is mourning the death of her husband from sickness, saying "if only he'd taken this medicine...". To complete the sidequest, just travel back in time with the medicine and give it to the husband (saying it's from his wife). Both husband and wife will be mystified about how you knew and where it came from, as the wife hadn't told you yet about her husband, but that fixes the future so they both live and are grateful.
 * Pretty much the point of TimeShift. The Big Bad gets the suit that lets him time-travel at will and reshapes the world to his own ideals, so the Hero has to get the toned-down suit and go back after him in order to try to fix things.
 * Singularity has the main character trying to do this after a time-travel incident leads to
 * Millennia Altered Destinies is built on this trope. You play a human cargo ship captain who is abducted by an alien race called the Hoods and given a timeship with the goal of stopping the hostile Microids from taking over the Echelon galaxy (except that they have already done that in this timeline) and moving on to the Milky Way. To this end, you are to seed four suitable planets with life and help the four different races evolve and deal with various crises. Your ship, the XTM, can go back 10,000 years into the past in 100 year increments. You also have access to the complete history of the four races that, unlike you, doesn't have Ripple-Effect-Proof Memory. This means that, as soon as you change something, there is a temporal storm that updates the database right before your eyes. Essentially, you have 2 goals in the game: help the 4 races spread out throughout the Echelon galaxy in equal amounts (defeating the Microids) and have the 4 races reach the technological stage at which they can build replacement parts for your ship's wormhole drive to get back to Earth. Due to the game mechanics, you usually can only accomplish one of these.
 * Unfortunately, there is an alternate version of you, who has been recruited by the Microids to stop you. He will randomly show up at any point in the past to destroy one of the races, undoing all your hard work. You can't kill him, just as you yourself can't be killed.
 * Interestingly, the creators originally planned to have a Nonstandard Game Over if you happen to have screwed up the history of the four races so much that it can't be fixed. Your ship would be destroyed by a powerful temporal storm. Then they realized that this could never happen in-game, and eventually removed that ending.
 * This is intention in Undertale: use their newly gained powers to destroy the time line and redo everything that wemnt wrong after.

Visual Novels

 * This trope is the entire purpose of the game Time Hollow, where the main character is completely normal except that he can use his "Hollow Pen" to make a window into the past and alter an event.

Web Original

 * The "Strangerverse" in AlternateHistory.com has its basic premise as this.
 * In the United States of Ameriwank, the traveler came to Colonial America before the American Revolution and gave George Washington a mission to unite the world under the United States to prevent an apocalyptic war.
 * Almost all of the Strangerverse stories take as their basic premise that there was an apocalyptic war shortly before 2258, and that a group used prototype time-travel technology to send one person back in time long enough to hand over a few tools to an historic figure and tell the recipient why he is doing so. Just when and where the Stranger travels to, what tools are delivered, and whether the destination was the intended destination provide the -verse part of the Strangerverse.

Western Animation

 * Samurai Jack: "Now the fool seeks to return to the past, and undo the future that is Aku..."
 * This is Time Squad's mission; to keep the past from unravelling. However, all of these changes are comedic and none ever cause a bad future. They just have to be fixed.
 * The Peabody and Sherman segments of Rocky and Bullwinkle involve going back in time to correct historical events which have gone wrong.
 * This sets the events of Megas XLR into motion through subversion of the trope. The Human Resistance steals a prototype Glorft mecha, modifies it, and attempts to send it and its pilot back in time to prevent the Glorft from winning the war against humanity. Things don't go as planned, and as a result the Glorft invasion actually happens centuries before it's supposed to. Hilarity Ensues.

Anime and Manga

 * In the Mahou Sensei Negima manga, this is Chao Lingshen's motivation for messing around with her great grandfather's childhood, although whether she had an absurdly complicated Xanatos Gambit set up, or was simply playing Xanatos Speed Chess as her alterations made foreknowledge less useful is never made clear. She actually fixed the problem she went back to solve with the changes wrought by her first trip, but later makes a second one to tie up a loose end or two before the Cosmic Deadline.
 * Subverted in Dragonball Z. Future Trunks also attempts to Set Right What Once Went Wrong, but he does this in a timeline not his own: since in DBZ every timeline counts as another dimension, any changes made in the current time will not directly effect Future Trunks' past or future. He still wants to help out, hoping to create at least one peaceful world, and to return to his own time strong enough to finally stop what he wanted to prevent.
 * Archer in Fate/stay night attempts to do this by creating a Temporal Paradox. Archer is not so much setting right what went wrong as setting wrong what once went really wrong.
 * A great part of the Haruhi Suzumiya Light Novels deals with Kyon trying to rectify past events in order not to let Haruhi's powers go haywire. Although he travels back in time mainly to set Haruhi off so that she'd create aliens, time travellers and ESPers, and to fix up the events on December 18. On that day, there's a point in time where there's 3 Mikurus and 4 Kyons. December 18 was only because of Disappearance, and to fix what Yuki did.
 * Yakitate!! Japan: Kazuma's last bread of the second Tournament Arc is so amazingly delicious, it sends the judge back in time to RetCon his own mother's death.

Comic Books

 * Rayek from Elf Quest travels to the future in an attempt to 'save' his space-travelling ancestors from being thrown back in time and crashing on the planet. Unfortunately, all their descendants currently living on this planet will then cease to exist—and will never have existed, since their ancestors will never have set foot on the planet in the first place. Opinions about whether or not this is a good thing differ—he thinks it's good, everyone else thinks it's bad. Who cares about other men's opinion anyway. He tried to compromise by having the people he actually knew and cared about stay inside the palace, which would protect them from the history-wiping effects... but since this would only save the people standing immediately in front of him, and still wipe out everyone else on the planet, they refused his offer.
 * In the "Camelot Falls" storyline in the Superman comics, a prophetic sorcerer tells him what he needs to do to avert the extinction of humanity years down the line. In a subversion of this trope, Superman refuses to comply, namely because "what he needs to do" involves not preventing the deaths of countless innocents.
 * The mission of Samaritan in Astro City. He actually did set things right before the series started, but now his own time period has changed beyond recognition.
 * Cable has apparently set as his ultimate goal to set right everything that went wrong, like preventing Apocalypse from waking up. (He then wakes up Apocalypse himself by accident. Good job.)
 * Similar to Cable, Bishop's goal is to prevent the dystopian future he comes from. Only problem is, he's never been sure exactly how.
 * Archie's Sonic the Hedgehog series:
 * Silver's personal Story Arc is much the same as in |Sonic the Hedgehog 2006—he comes from a Bad Future where the world is all but destroyed, and is constantly traveling through time trying to find a way to undo it, with his only clue being that the betrayal of a member of the Freedom Fighters was somehow key to this disaster. Of course, like his game counterpart he's being advised by a -- supposedly reformed --- villain, so we'll have to wait and see how that turns out.
 * A Story Arc in the early 100's issues involved Knuckles' future daughter Lara-Su attempting to undo her own Bad Future by preventing her father's assassination. Unfortunately, when she got back to her time, she discovered that her mother had lied to her in order to protect her—the truth was, Knuckles hadn't died, he'd pulled a Face Heel Turn and was in fact responsible for the Bad Future they lived in. The bright side, however, is that the "present" Lara-Su had visited was the series' main timeline, while her future is an alternate one. So we don't have to worry about our Knuckles switching sides like that.
 * In the Star Trek "Time Crime" miniseries, someone screwed up the timeline so that Klingons aren't aggressive warmongers and the Romulan Empire doesn't exist. Despite the positive bits, Kirk and Spock still have to fix everything because the overall outcome would ultimately be a Bad Future. That and, as bad as Romulans are, they don't deserve to be erased from time. In one Tearjerker moment, Kirk realizes that "fixing" the timeline will mean losing his son David (in the real timeline David was killed by Klingons), and he gives his son one final hug before embarking on his trip through time.

Film

 * In Galaxy Quest, the "Omega 13" device is used to go back 13 seconds in time, "enough to change a single mistake".
 * In the conclusion and epilogue of Jumanji, Alan prevents Carl Bentley from getting fired (or gets him re-hired), and the kids' parents are stopped from going on their fatal ski trip.
 * This is the main plot of Star Trek: First Contact. The past is going perfectly fine until the Borg try and set wrong what once was right.

Literature

 * Animorphs:
 * In Elfangor's Secret, the team is sent back to prevent Visser Four from changing key events in the past.
 * In In the Time of the Dinosaurs, they must sabotage a nuclear device and sacrifice an entire colony of aliens, or else the Cretaceous Era won't end on schedule.
 * In the novel Soon I Will Be Invincible, Lily gets sent back in time to prevent a blight from wiping out humanity, but after she succeeds she decides she liked the blighted future better and becomes a supervillain to try to bring back her original future. However, this turns out to be an outright lie—she's a native of the current time period, although the era she claims as her origin really is a possible future that she has visited—and she ends up using it to trick another supervillain into saving the world.
 * In Harry Potter and The Prisoner of Azkaban, Harry and Hermione have the chance to go back and save two innocent lives.
 * Dean Koontz's Lightning

Live-Action TV

 * Naturally, Life On Mars and Ashes to Ashes have played with this: in Sam's case, it was finding out why his father abandoned him, as well as arresting the serial killer who'd kidnapped his girlfriend and a crime lord who'd had a witness in his custody murdered; in Alex's, it was preventing her parents' death by car bomb. Their success rates are... varied; Sam eventually wound up convincing his father to skip town, because there was that little matter of a murder and racketeering charge if he stayed...
 * Doctor Who
 * Officially this can't work in the Whoniverse (the series 1 episode "Father's Day" shows why) but Amy gets a chance to do it in a small way in the series 5 finale—not by time travelling, but because.
 * Not-quite-subverted in "Genesis of the Daleks". The Time Lords send the Doctor back in time to the creation of the Daleks, with the goal of either preventing their creation, or at least making them less aggressive. While there, the Doctor is captured by the Daleks' creator and is made to detail every Dalek vulnerability he knows about. Being the universe's resident expert on fighting Daleks, this would have been a catastrophe had he not destroyed the tape before leaving the scene.
 * Possibly subverted in "Resurrection of the Daleks", where the Daleks used the Doctor's interference in their creation to justify an attack on Gallifrey.
 * Russell T. Davies' view was that this Dalek-Time Lord skirmishing eventually led to the Time War of the new series, thus subverting the trope. Alternatively, this could be playing the trope straight, as the Time War may actually be a better outcome than what the Time Lords originally predicted.
 * In the Mirror, Mirror series, there is exactly one person who was trained to do this exactly once, as revealed in the final episode. Everything prior to this point had already happened in her mentor's past.
 * In Babylon 5, this is a key point in the five-year plot—instead of "Sometimes, trying to Set Right What Once Went Wrong is what sets everything wrong in the first place, resulting in a Stable Time Loop.", everything will go wrong unless the heroes go back to keep what's right, creating a Stable Time Loop by altering the past to what it is. Which gets really confusing if you try to ask, "What happened the first time?". There are a few hints via dreams and a broadcast. It's said the Shadow's army would have been three times larger and more prone to act directly earlier.
 * More of a case of "Set right what we messed up" but in an episode of Hannah Montana, Miley and Jackson travel back in time and mess up their parents meeting. Cue a back to the future style disappearance for Jackson as Miley tries to set things right. It was probably All Just a Dream.
 * Done in Power Rangers Turbo, with heavily debated success. A robot, the Blue Senturion, came from a thousand years in the future to warn the heroes about a war two years later... and was intercepted by the villains, who took the message, and deleted it from his memory. Not only did the war still happen, but it happened a year earlier than scheduled. On the one hand, an all-out win for Team Evil was averted, but on the other, it still didn't end very happily.
 * This is Desmond's major character motivation throughout the third season of Lost (apart from his desire to be reunited with his lost love Penny).
 * Farscape
 * Subverted in episode "Different Destinations," where the team go back in time to a historic siege and make things worse by getting everyone except them killed.
 * Played straight in "Kansas" when the team accidentally goes back to Earth in 1985 and has to prevent John's father from going on the "Challenger" shuttle to prevent his death and John possibly never ending up on Moya.
 * Guinan of Star Trek: The Next Generation is practically this trope walking personified (as for reasons that were never even hinted at until The Movie, changes in the timeline do not affect her), especially in "Yesterday's Enterprise". More technically they don't entirely affect her. She could identify something was wrong, but didn't know what could have caused it.
 * The Outer Limits TOS episode "The Man Who Was Never Born". A mutant from a devastated future goes back in time to prevent the biological disaster that destroyed civilization.
 * In modern series of The Outer Limits. A scientist develops a time machine and uses it to go back and kill serial killers before their first murder. However, it turns out she was motivated by the fact that she'd been raped and tortured by a serial killer herself as a child. She eventually goes back and kills him, thus saving her younger self, but this undoes all of her other killings.
 * She also dies while killing him. However, her younger self realizes that time travel is possible and uses it to re-invent the technology. This time using it to help people.
 * Another episode involves a popular presidential candidate traveling on a plane and seeing an intangible image of a woman claiming to be from a Bad Future where his plane crashed (because of another time traveler's accidental interefence), and his ineffectual opponent ended up winning. She convinces him to jump out of the plane by claiming that she will use future technology to halt his fall moments before hitting the ground. This appears to happen, but then she explains that she is here to kill him, as he is the one who will become President Evil due to his paranoia. The falling scene repeats, and nobody catches him this time. The plane lands without problems.
 * Supernatural has an episode that Dean thinks is a Set Right What Once Went Wrong, but not only does it turn out he was only meant to Witness What Went Wrong and not change it, it sure looks like he actually caused it.
 * Another episode had an angel go back to that time to try to kill their mother before they were born. While she seemingly succeeds in killing their father, he is brought back as a vessel for Archangel Michael, who kills the angel.
 * Stargate SG-1
 * Subverted in "The Gamekeeper": Jack and Daniel think that they're being sent to the past to fix mistakes in their lives, but it turns out that they're just mentally reliving them, not really time travelling, and there's no way for them to fix it anyways.
 * Played straight in the Aschen arc, in the episodes "2010" and "2001". The former takes place in a Bad Future, where the Aschen, posing as benevolent aliens, infect Earth with a sterility vaccine that will eventually cause its population to die out. To avert it, SG-1 sends a note to their past selves back in time, leading to a less tragic future.
 * Played straight in the two-parter "Moebius" when an attempt to go back in time to retrieve a piece of technology results in screwing up the timeline and having to go back in time again to fix it.
 * Not necessarily. It's not made clear if it was SG-1's interference that made Ra leave with the stargate or if that was what originally happened.
 * Also played straight in the movie Continuum as listed in the "Films" section.
 * The Stargate Atlantis episode "The Last Man" has Sheppard thrown 48,000 years into the future, where a program Rodney left behind recounts a long It Got Worse story of the intervening years and arranges to send Sheppard back to fix everything. He even gives Sheppard some crucial information, like Teyla's location at the time, so Sheppard can change what happened for the better.
 * The X-Files episode "Synchrony" presents the case of a strange old man warning an MIT student and professor that the student is going to die at a specific time—because of this warning the professor, attempting to save the student, ends up accidentally pushing him into the path of an oncoming bus and thus the warning is a Self-Fulfilling Prophecy. The old man is  attempting to Set Right What Will Go Wrong and prevent an impending scientific breakthrough   Mulder cites an old theory of Scully's about how You Can't Fight Fate, and so the old man's efforts are probably doomed.
 * The conclusion of the Star Trek: Voyager "Year of Hell" serial. Or for that matter, the conclusion to the series altogether.
 * In an episode of The Flash, Barry Allen is accidentally thrust ten years into a future where Central City has been taken over by his brother's killer, Nicholas Pike, and where an underground group of citizens were waiting for the Flash to return in order to set things right.
 * Kamen Rider Den-O touches on this occasionally, in the context of "You are not supposed to do this".
 * Kintaros nearly gets kicked off DenLiner in one episode when he tries to change a girls past for the better instead of dealing with the Monster of the Week (who was damaging the timeline himself in the meantime).
 * Although it seems perfectly okay for them to change history in some cases but not in others. In one early episode, our heroes help a struggling musician make it to a gig which he had missed in the original timeline. He's convinced that had he not missed this gig, he'd be a star in the present. Turns out he's still a nobody even after they change history; the only difference is that he no longer blames himself for the breakup of his band. Since the change was so unimportant, our heroes are informed that what they did was okay.
 * What the previous two events have in common is that the change prevented the Imagin from making a Deal with the Devil with that person in the first place. While Singularity Points negate some of the damage caused by an Imagin to the past, they only negate damage to things that were part of their memory and some things are lost for good. So completely negating the rampage better preserves the timeline than simply destroying the Imagin in the past, even if it requires a minor change. Strangely, this doesn't negate the fact the Imagin was destroyed though...
 * In the Non-Serial Movie of Kamen Rider Kiva, King of Hell Castle, Wataru goes back in time in order to prevent a prison inmate from discovering the ruins of an ancient demon race and becoming their king. Unfortunately, his actions don't make any real difference, and in fact may have made it worse, given that when he returns to 2008, the creatures are roaming freely and the moon is covered by a gigantic monster eyeball.
 * In Primeval, Matt spends the majority of season four and five doing this to prevent a Bad Future.
 * The Mysterious Ways episode "Yesterday" deals with a police officer who relives the previous day after accidentally shooting and killing his partner and praying for some way to make it right.
 * Lois and Clark; in the episode that occurs right after the title characters' wedding, their honeymoon is interrupted by a Time Traveling scientist who warns them of a vile curse placed on both of them in their previous lives (yes, Reincarnation Romance is a big plot point here, go figure), one that will kill Lois in every successive life when she and Clark consummate their marriage. Traveling back to the origins of this curse (in Medieval times, where Clark is this reality's version of Robin Hood), they find it was orchestrated by Tempus in his previous life. (Lois is actually a little surprised it's him and not Lex Luthor.) Because Clark does not have Superman's powers here and the sorcerer who curses them is far too powerful to fight, the pair decide the only option is to let Tempus win, as then he would have no reason to enact the curse. Unfortunately, this messes up the "spiritual timeline", so to speak, leading to Tempus' victory in all successive timelines. So the scientist enacts plan B, and they travel to a timeline between the first and the present (the Old West, where Tempus has no access to such powerful magic) and defeat him there.

Web Animation

 * Red vs. Blue uses the Stable Time Loop variety of this trope. When Church is blasted into the past by a nuclear explosion, he uses the opportunity to try and correct each disaster that has occurred in the series up to that point. Of course, it turns out he's the cause of most of them, including his CO's mysterious heart failure, numerous injuries to his teammates, and his own accidental death ("Oh my god! I'm the team-killing fucktard!"). When his every attempt to prevent the bomb from going off fails, he eventually gives up, makes sure a copy of himself is blasted into the future with his teammates, and delivers a bitter Aesop about accepting reality as it is.

Tabletop Games

 * The Ravenloft boxed-set adventure "Castles Forlorn" sends the heroes to a haunted castle which shifts repeatedly between three time periods. They have the opportunity to free an imprisoned woman while in the second of these eras, which causes corresponding historical changes to the third.
 * The notorious Champions module "Wings of the Valkyrie" combines this and the Hitler exemption and setting things wrong: the player characters need to travel back in time to save Hitler; a previous traveler had ensured Operation:Valkyrie's success, expecting this would cripple the Reich. It didn't work; the Reich's new leadership was just as evil, and much more capable.

Video Games

 * In the MMORPG City of Heroes, several factions are attempting to do this, but their concepts of "right", usually focusing on self-preservation, were often mutually exclusive.
 * The temporal organization Ouroborous gave player characters the ability to do this to their own timelines with pretty much no oversight at all.
 * In Pokémon Mystery Dungeon: Explorers of Time and Pokémon Mystery Dungeon: Explorers of Darkness, before ending up in the past with amnesia the player character was part of a team that has come from the future to prevent time from stopping. Succeeding in the mission causes a Temporal Paradox, causing both you and everyone met in the future to cease to exist. Except then the partner you met at the beginning of the game angsts until Dialga decides you do get to exist after all.
 * Subverted numerous times in the Prince of Persia series. In fact, these subversions are the driving force for much of the Prince's story.
 * In Chrono Trigger the characters end up warped to After the End and, upon watching a video of The End itself, resolve to stop it happening. They only have one chance because, well, they die if they don't do it right. Also a rare example where the Temporal Paradox part of succeeding is actually acknowledged; a paradox is caused because the heroes learn of the end from records after it happens, and then alter the future so the end which produced those records never comes into being. Chrono Cross is essentially an entire game about a whole cornucopia of consequences resulting from this, none of which are pretty.
 * The world of Dragon Quest VII used to be a vast and expansive place, but by the time of the game, it has been reduced to a single continent. Your party's mission is to travel back in time to the continents which once existed in the past and stop the various disasters which destroyed them, thereby causing them to reappear in the present.
 * In Dark Cloud 2 you had to restore various points in the future that were destroyed in the past by the Big Bad.
 * Kain's motivation during the later Legacy of Kain games is to fix the ruined world he himself created by traveling through time, although the plot is so complex and nearly every member of the cast is such a conniving manipulator that the importance of this, while not lessened, is somewhat drowned out. The rules of time travel in this setting make this goal even harder than it usually is; normally, You Can't Fight Fate and going back in time will merely cause a Stable Time Loop, but real alterations can be made by deliberately causing a Temporal Paradox and then acting inside of its effect.
 * Used in |Sonic the Hedgehog 2006:
 * In Sonic's story, he eventually ends up time-traveling to a Bad Future, and discovering that it was caused by the death of Princess Elise, very shortly after the date that Sonic had just left. Sonic travels back to rescue her.
 * In Silver's story, Silver is a native of the aforementioned bad future; he travels to the past (i.e. Sonic's time) intending to kill the "Iblis trigger" and prevent Armageddon. However, he thought that Sonic was the Iblis trigger—because Silver's source of information about the past was manipulating him into Making Wrong What Once Went Right.
 * The plot of Ratchet and Clank Future A Crack In Time.
 * Fails spectacularly in The Legend of Zelda series.
 * In The Legend of Zelda: Ocarina of Time's ending, Zelda sends Link back to the beginning of the game so he can avoid his Nice Job Breaking It, Hero moment. Rather than changing the future they're in, it creates a second time line. The timeline where Link sealed Ganon away now lacks a hero to take care of him, and the gods end up destroying Hyrule in a Great Flood for lack of any other option. And the other timeline, where Link didn't lead Ganondorf directly to the Triforce? Ganondorf ends up with 1/3 of it and gets sealed away anyway. Net result of attempt to Set Right What Once Went Wrong: one timeline in exactly the same situation that they were trying to prevent, and one timeline utterly destroyed.
 * The Legend of Zelda: Majora's Mask begins with Link dumped into an alternate reality, unwillingly transformed into a harmless Deku Scrub, and forced to watch helplessly as the world around him goes to hell in a handbasket before its eventual destruction at the end of the third day. Then Link goes back in time, regains his true form, and relives the same three days over and over as he gradually meets and helps everyone the Big Bad has hurt, until he is finally strong enough to stop it all from happening.
 * The entire plot of Mortal Kombat 9 centers around an attempt to do this. Shao Kahn ends up winning the events of Armageddon, leading Raiden to send a message back to his past self to try and fix this.
 * Deconstructed in Episode 4 of the Back to The Future games, where.
 * Riven has a non-time-travel variant as the framing device. The linking books the series relies on can be used to modify worlds they link to using quantum uncertainty; if it could have been there but was never noticed before, writing in that it is there will make it happen. Unfortunately, Gehn, who wrote quite a number of linking books, was not actually very good at writing them, so the same quantum-uncertainty mechanics are causing the Ages he wrote to deteriorate of their own accord. His son, Atrus, is much better at writing them, and thinks he can save some of them using these same quantum-uncertainty mechanics, but some are beyond salvaging. Your task is to go into one of the doomed ones to rescue Atrus' wife while he stays and tries to stall its destruction for as long as possible.
 * This is the reason for (most of) the Caverns of Time in World of Warcraft. The Infinite Dragonflight are screwing with history and the Bronze Dragonflight are recruiting mortals to help them out, since they're too preoccupied searching for their missing leader Nozdormu.
 * This is part of the theme around in Undertale

Web Comics

 * Played completely straight in Schlock Mercenary, right down to the "only one chance."
 * Inverted in Chainsawsuit, with The Time Ruiner!
 * Done as part of a Terminator homage in Sluggy Freelance when Berk arrives from the future to stop K'Z'K from conquering the world.
 * Done in General Protection Fault in the "Serruptitious Machinations" Arc.
 * Bad Future in Homestuck uses his Time Travel ability to try and stop John from being a gullible idiot. It appears to have worked and the protagonists get a lot of sweet loot from the future out of the deal as well.
 * Bug shows us that if you attempt to set right what was once wrong, you risk doing just the opposite. You can also use this trope to end a relationship.
 * Yehuda's motivation for working as a bike mechanic in Yehuda Moon and The Kickstand Cyclery.
 * Late in the course of Narbonic, Artie and Mell discover a secret tape that was sent from a Bad Future. Future Mell did a host of bad things including becoming vice-president and then having the president assassinated, all so she could use one shot at time travel, even though it would kill her and destroy the universe. Her goal? To save Artie. She thinks that killing protagonist Dave Davenport will fix things. And she is wrong.
 * The Non-Adventures of Wonderella had the protagonists use time travel again here, and this time they gave William Shakespeare stage fright, and then tried to reconstruct his following works. The result is rather predictable.

Western Animation

 * The Fairly OddParents, episode "The Secret Origin of Denzel Crocker". Timmy's attempts to stop his teacher from growing up to become a fairy-obsessed maniac result in him lamenting, "NO! This is exactly what I was trying to prevent!" To clarify  At least he stopped the election of President McGovern.
 * The first Futurama movie "Bender's Big Score" deals extensively with time travel, ending with Bender going back to the year 2000 with the tattoo on the time duplicate Fry's ass to put the tattoo back onto past-frozen Fry's ass in the first place, for any of the plot to make sense.
 * In the '90s X-Men animated series:
 * Bishop traveled from the future to the present on three separate occasions to prevent a Sentinel-ruled dystopia from coming to pass. On the second trip, Cable travels from even further in the future to stop Bishop from inadvertently making the far future worse.
 * Bishop is terrible at this though, mostly due to his trigger happy nature. His plans to just kill/destroy the source of the problem and then head back to the future never work because he doesn't unravel the conspiracies involved. Fortunately his actions let the X-Men know, and they do manage to fix things.
 * Back to The Future
 * "Go Fly A Kite". Verne accidentally interrupts Benjamin Franklin's famous kite experiment, causing the electricity in present day Hill Valley to disappear. Doc and Marty must head back to 1752 and simulate a storm in order for Franklin to make his discovery.
 * Played straight in "Ok at the Gunfight Carol" episode of Captain Planet: Hoggish Greedy & Sly Sludge, travel back to the Old West to get the deeds for the Grand Canyon turning it a landfill. The Planeeters follow and work things back on track returning the Grand Canyon to it's natural state.
 * Danny Phantom promises not to allow his evil future to come to pass after seeing himself as a sadistic, mass-murdering sociopath. Although Clockwork helps, the subversion comes when it's hinted at the end that it may just be a matter of time after all, if with different circumstances.
 * Future Candace travels back in time after she discovers that her meddling with the timeline has turned the tri-state area into a dystopia ruled by Doofenshmirtz in the Phineas and Ferb episode "Phineas and Ferb's Quantum Boogaloo".
 * This is the goal of Nox, the Big Bad from season 1 of the French cartoon Wakfu. His desire to save the family that he lost 200 years before the show has driven him to go from a simple watchmaker to one of the most powerful (and insane) magic users alive. Unfortunately, while he is a skilled enough time mage to slow time to a stand still, he has so far been unable to actually travel backwards in time. He believes that this is a power requirement issue, and now seeks to drain enough wakfu from the plants, animals, and people of the world to save his family. One character mentions that he has drained entire countries dry over the years, and his current plan involves exterminating an entire race of people to gain the wakfu he needs. Of course, Grougaloragran also mentions that . Nox, however, is long past caring.
 * In Jonny Quest: The Real Adventures episode "The Edge of Yesterday," we learn that Dr. Quest created a time machine program in Questworld after his wife died, which would allow him to travel back in time and see his wife again. When he finished it, he realized he wouldn't only be able to see his wife, he could also change the past to prevent her from dying. His ethics would not let him alter history for personal gain, so he sealed the program so it couldn't be used. Later on, Jonny and Jessie use the program to go back in time and prevent Ezekiel Rage from planting a bomb that could cause the tectonic plates to split, destroying the Earth.
 * Two episodes of Lilo & Stitch: The Series centered around this plot. In the first, Lilo embarrasses herself in front of her love interest. She find out Jumba has a surfboard style time machine and used it to fix the blunder, but at the same time there's an experiment running around that Stitch tries to catch and each attempt causes a disaster to the area causing multiple re-dos. Eventually Lilo has to let herself get embarrassed to fix the timeline. The second involves Lilo finding an experiment that can warp time forward, allowing her to age into a teenager and later an adult. However since she and Stitch are time traveling, they're not around to catch experiments. Allowing Big Bad Gantu and Hamsterveil to capture them and take over the Earth. Conveniently said experiment has a Reset Button but they have to rescue it first to fix the damage.
 * Family Guy
 * Done as a Shout-Out to Back to the Future, when Peter has Death warp him back in time so he can relive a day in his teenage years. However he does so at a critical moment in the history of his relationship to Lois that ends with her married to Quagmire and him married to Molly Ringwald (its complicated, just go with it). Peter, along with Brian, convince Death to send them back to undo Peter's mistake.
 * Also, explicitly referenced in an episode where Peter becomes a Jehovah's Witness (among other things) and explains Jesus like this, leading to a Quantum Leap sight gag.
 * And now Stewie and Brian are credited as using this to create the Family Guy universe. Literally. So that's a... set half-right what was elsetime random-in-the-void? It gets played straight in the same episode when Stewie's sperm-brother tries to erase one of his more 'European' ancestors to erase Stewie.
 * Likewise, sister series American Dad had a Christmas Episode that featured a Ghost of Christmas Past trying to pull Yet Another Christmas Carol on Stan but he uses the opportunity to try and "fix" Christmas by killing Jane Fonda. His guardian angel stops him, but when they get back to modern times America is under the control of Soviet Russia. It Makes Sense in Context.  Note that even in the end the timeline isn't the same: