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The Time Traveller's Dilemma

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"You see, Jake, there's rules to this stuff. Wishing an event to be changes elements before and after it; memories will be destroyed, babies will not be born, potential worlds could be evaporated by your wish."
Prismo, Adventure Time

So you've decided to Set Right What Once Went Wrong. Temporal Paradox is not a problem; once you make this change, the dark future (your old present? Whatever) will utterly change.

There's a very dark possibility of a Sadistic Choice here. What if there's no such thing as In Spite of a Nail? What if the holocaust you're trying to prevent resulted in someone being born who will no longer exist if the situation of his parents getting together changes? What if there's millions of people who will be changed or erased against their will? What if this timeline had someone do a Heel–Face Turn who won't in the new timeline?

This is a heavy responsibility.

Many writers don't like dealing with this, so they'll often write that the better future is better in every way imaginable with no exceptions; and nobody left out. Or that The Multiverse means that world, those people and its choices somehow still exist... somewhere. But not everyone does, and it's a disturbing train of thought.

One must keep in mind that people already make choices that prevent future possibilities from happening every day. Preventing future possibilities from happening is inherent in the act of making choices at all. For example, by sitting in your room and reading TV Tropes rather than going out and having as many babies as possible, you are denying the existence of many potential people, but you can hardly be held responsible for the deaths of many because of that. The major difference between everyday decision-making and the situations examined by this trope is that the people subject to it have experienced the alternate timelines themselves; that can certainly change the perception of the people who have to make the decision.

Reset-Button Suicide Mission is closely related, but in that trope the erasure of events is often seen as a positive, negating the costs paid to push the reset button. The two can intersect in painful ways, however: Say, Alice and Bob have a child, Charlie, in the Bad Future, but never would have gotten back together without the cataclysm they want to undo. Thus, their chance to change the past becomes a Sadistic Choice between Charlie's existence and the lives that would be saved by changing the past. Needless to say, Taking a Third Option where the positives can be kept while erasing the negatives is very popular when the two tropes overlap.

Related to Expendable Alternate Universe, The Story That Never Was. Hitler's Time Travel Exemption Act is the most quoted example of this trope.


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    Anime and Manga 
  • The Series Fauxnale of Ayakashi Triangle before it changed magazine has Suzu sent back in time to the day Matsuri was turned into a girl in the first chapter, and her inner ayakashi medium urges her to stop it from happening. Suzu goes along but pulls back at the last second, as she realizes Matsuri's transformation had been key to his growth as a person and most of the relationship he'd since formed. (Considering it lead to Shirogane's Heel–Face Turn and directly saved Matsuri's life once, the consequences of changing the past could have been far worse than Suzu realized.)
  • Kyon of Haruhi Suzumiya once changed the world back to his old one via Time Travel. He still has nightmares of the implications of what he did, mostly because it was a world where Yuki Nagato had her fondest wish: being human and quite possibly in love with Kyon.

    Comic Books 
  • In the "Age of Apocalypse" arc of Marvel Comics, set in a changed present where Charles Xavier was killed in the past, Magneto and Rogue have a son. The Time Traveler Bishop wants to change things back. Magneto supports Bishop in this, but reminds him that if they succeed, his son will be gone forever. Presumably this also bothered some writers, who later wrote that this world continued to exist as an Alternate Universe. (Btw, Jean Grey stopped the nukes in the end.)
  • The DCU explored part of this with alternate timelines where good versions of Doomsday and Vandal Savage change things back; ironically back to where they are villains.
  • The end of Neil Gaiman's Marvel 1602 sets right the circumstances that caused the temporal divergence that brought about the 'Age of Marvels' in the Elizabethan era. Thus, the timeline is overwritten, and history proceeds as necessary. The Watchers, however, step in and save the 1602 world as a pocket universe, kept in a glass globe by this version of Uatu.
  • Astro City:
    • Samaritan changes the future into a utopia, but his family was never born, and his old house is replaced with a future Taco Bell.
    • It's revealed in "The Eagle and the Mountain" that this is actually one of Samaritan's powers. No matter what happens in history, he will still exist.
    • One of the most famous issues, "The Nearness of You", has a different version, where a man is haunted by dreams of a woman he never met. In a previous timeline, she was his wife, but following an off-panel Crisis Crossover, she was erased from existence, leaving only his memories of her.
  • The DCU's second Chronos spent some time trying to change history so his mother wouldn't die in a car accident. He eventually realised that the only way to ensure this was to never be born. He still exists as a time traveller, but his history up to the point he found Chronopolis has gone.
  • In the JLA/Avengers story arc, at one point the histories of the DC and Marvel universes were altered by the retroactive effects of a history of the two universes interacting through their respective heroes. When they realized it needed to be fixed, they first asked to see what they were saving. Barry Allen and Superman saw their deaths, Hal Jordan saw that he would become the power-mad Parallax, Hank and Janet Pym saw Hank striking Janet, etc and they realized they were deciding the fates of potentially billions of people. The heroes decided to go forward in spite of what would happen to them.
  • The cost of salvaging anything at all of the original multiverse in Crisis on Infinite Earths was to produce a new single universe and erase the original multiverse entirely from history. So, from a very real standpoint, nobody survived the original Crisis (except Superboy Prime and co., and maybe Power Girl and Psycho Pirate), and all the current heroes are temporal copies of the originals.
  • The Young Avengers team was started by the time-traveling villain Kang the Conqueror, who got a look at what he was going to grow into and ran away to our time to try and avoid growing into him. Which he did apparently succeed in, but unfortunately no Kang meant that none of the many fights he'd had with The Avengers over the years and in some way that lead to almost all of them being killed, the small amount of the alternate world we see looking pretty dystopian, and the members of his team who were children of Avengers members (except for the daughter of the one whose death might actually have been prevented in the new timeline) fading out of existence. He realized that he had to go. Although we've found out since that he's still time-traveling trying to find a way to avoid becoming a villain, he's just looking for a way that won't wreck things for everyone.

  • In Memento Vivere, a Final Fantasy X fanfiction, this is a main plot point of the story.
  • A Fullmetal Alchemist Slash Fic called Redo explores this problem. Ed and Al, living 20 Minutes in the Future from the end of the manga/Brotherhood, are sent back in time by a rogue alchemist to right before they traveled to Lior. They struggle with how they're now given the opportunity to save some people who died and situations they screwed up the first time, but also need to make sure everything that went right before does as well.
  • Averted in The Three Whooves, where Three's memory is erased to make sure his experiences don't change his actions.
  • This weighs on Edward throughout My Master Ed. If Ed manages to save Xerxes, Amestris as a country won't exist. If Hohenheim never becomes immortal, he won't live long enough to meet Trisha, and Alphonse will never be born. Ed is acutely, painfully aware of this.
  • Discussed in A Student Out of Time, where Hajime Hinata and a few others is sent back in time and decides to try and stop the events leading up to The Tragedy. He and his allies are aware that, as horrible as it is, they're also essentially erasing the events that would lead to a lot of people becoming heroes and having families of their own. Later on, Umeko, who's learned her future self is the one who invented time travel, concludes that if they do change enough, the Tragedy future and everyone there- including the minds of the past versions of the time travelers- will be overwritten by a new future.
  • In Stars, Eyes of Heaven, it's implied that Jotaro for years feared creating the Everybody Lives timeline following JoJo's Bizarre Adventure: Eyes of Heaven had Ret-Gone his daughter Jolyne, especially after getting into a relationship with Kakyoin and not knowing who her mom was (or learning that it was his platonic roommate Marian was his wife in the original timeline), which ended after the new timeline's Jolyne was born. In Demolition Man, it's revealed he had to consciously make sure his grandfather had his affair with Tomoko Higashikata so that Josuke would be born, despite repeating the same turmoil the Joestar family went through in the old timeline.
  • The Fate/Zero fic The Sage's Disciple has Crow confront Artoria with this dilemma to get her to realize the flaws of her wish.
  • In the Love Live! fic Nico Lost In Time, one of Nico Yazawa's goals after going back to when she was ten-years-old is to prevent her father's death from breast cancer. The dilemma is that she arrived before her younger brother Cotaro was even conceived, and the expenses of cancer treatment would delay or even prevent her parents' decision for a fourth child. Nico feels this dilemma is karma for playing God, but considers that any future "Cotaro" would at least grow up with both parents and still be loved by their older sister.

  • Considered in Avengers: Endgame as part of the plan to extract Infinity Stones from parallel timelines in order to undo Thanos' decimation of half of the universe. When in possession of the colossal, reality-warping power of the Stones, the team considers, but ultimately decides against the idea of retroactively undoing Thanos' acts, because such an act has far too much risk involved for what life has emerged in the intervening five years (including Tony Stark's daughter and countless other children born in the post-Thanos universe). In the end, they skip attempting any time-travel-based retcons, and their final priority is simply restoring the half of the universe that was originally dusted.
  • The ending of The Butterfly Effect invokes this trope: The main character goes back to the beginning, and ends his lifelong friendship/love (depending on the timeline in question) with the female lead before it starts. It works, but it's obviously a Bittersweet Ending. Which is still better than the alternate Downer Ending in which he chooses to kill himself.
  • Stargate: Continuum:
    • Subverted when the government in the new timeline refuse to help the team try to Set Right What Once Went Wrong. To punctuate this, the character who berates them was estranged from his family in the "good" timeline, but Happily Married in the altered one. And earlier, the alternate version of Colonel O'Neill that SG-1 encounters in the Arctic didn't tragically lose his son Charlie to a gun accident.
      Major General Hank Landry: My goodness, people, the arrogance of what you're asking us to help you do is mind-boggling!
    • And played relatively straight anyway once everything starts going to pot (Ba'al dies, snakeheads attack, Earth in deep trouble). Apparently, Earth humans (as opposed to "alien" humans) living as slaves under the Goa'uld is not to be thought of - and we'd be better off never existing in the first place.
  • X-Men: Days of Future Past touches on this in the extended "Rogue Cut". When Professor Xavier proposes sending Wolverine back to the 70s to change the past, several of the younger mutants wonder if they'll still exist in the new timeline. They ultimately agree with the plan anyway, since the current timeline is just so bad that they're willing to be erased to fix it.

  • Animorphs:
    • Averted in Megamorphs 3. Some things in the altered future may have been better, many things were worse, but in the end when Jake asked Cassie if they fixed everything, all Cassie could say was that "they put it all back."
    • In Megamorphs 2, this trope is in effect big time, though played...interestingly. To elaborate, the Animorphs go back to the end of the Cretaceous Era and soon discover not one but two sentient alien races who had colonized the Earth. They also soon discover that there is a giant freakin' comet flying through the sky, which Ax informs the group will just barely miss the Earth, based on its trajectory. The two alien races are at war with each other, but with the Animorphs' help, the "good" aliens drive off the "bad" ones. The "bad" ones respond by moving the comet off its path, aiming it towards the Earth in order to wipe out the entire "good" alien population. If you know anything about the age of the dinosaurs, you've probably guessed by now where this is going. The "good" aliens try a last ditch effort to blow the comet back into not hitting the planet and killing them all, but Tobias secretly has Ax rig the explosive to be a dud. Tobias insists that he did what had to be done, realizing that in order for humanity to rise, the Animorphs can't change history such that the "good" aliens (and the dinosaurs) survive, because they know from the lack of either in the present that they don't. Tobias also insists that he didn't consult the others because he didn't want them to live with the guilt of having condemned an entire sentient species to extinction. This still leaves Ax and Tobias with that guilt, and the question of whether dooming one innocent species to ensure their own existence was the right choice. This therefore is the unusual case of ensuring a Stable Time Loop being highly morally questionable.
  • Handily averted in John Birmingham's Axis of Time trilogy, where a multinational fleet from the 21st century ends up in the middle of World War II with no way to get back. The question is moot, as the appearance of the fleet results in a battle between them and the American task force heading for Midway. By the time the main characters figure out what happened, history has already been affected in a major way. Also, according to the novel, the characters know they're not really in their own past but in an alternate reality, so any changes they make will not affect their own timeline. For bonus points, Einstein himself confirms this.
  • Discussed and averted in Island in the Sea of Time and 1632, both novels involving the permanent transplantation of a modern town to the past. They came to the conclusion that it was a once-in-a-universe cosmic event, so they were astronomically unlikely to go back, therefore they didn't have to worry about changing the future because they'd already changed it by their very presence.
  • Addressed in Orson Scott Card's novel Pastwatch: The Redemption of Christopher Columbus, where the organization that just discovered time travel is quite aware that interfering with the past will erase the existence of everyone in the current timeline and insists on having the world vote on whether or not to Set Right What Once Went Wrong. As humanity is facing imminent extinction anyway at that point, the vote passes. It should be noted that, at first, they ask scientists to make sure that there's only one reality. This takes years, but eventually scientists confirm that time travel will not result in a separate timeline but will rewrite reality. How they can possibly confirm this is anybody's guess. The scientists also have to figure out how to send three people into the past at the same time. It has to be at the same time right down to the millisecond, as any difference would mean that two of the people would cease to exist along with this reality the moment one of them goes into the past. They make sure to measure the cables to be as identical as possible (despite the fact that an electrical impulse travels at the speed of light). Even then, the lead physicist admits that, in the end, they have to trust the universe to allow the "moment" to stretch to allow all three to make it through before reality is erased.
  • The Rifter: Faced head-on. John, by going to Basawar at an earlier point than the point where he got the key to the gates from Kyle, changes history (and creates an alternate version of Kyle who never traveled to Nayeshi and lost the key); on the whole, the new history is for the better (thanks to American liberalism, the power of love, and perhaps the providence of Parfir), but bad things happen too — for example, John destroys northern Basawar and all its living things, which wouldn’t have happened in the original time.
  • In the Peter David Star Trek Expanded Universe novel Imzadi, Admiral Riker wants to go back some thirty years to the time of late-season TNG to save Deanna's life, since he believes someone already altered time by traveling back to kill her; Data objects on these grounds. When it's done and everybody has time-traveled home, the Guardian of Forever—time-travel mechanism of choice today—points out that "All is as it was." When asked why it didn't bother to mention that yes, Riker was restoring the proper flow of history, it answers You Didn't Ask.
  • In the Time Patrol short story "Delenda Est", rogue time travelers interfere with the outcome of the Punic Wars, resulting in a present that's nearly unrecognizable to the Manse Everard and his fellow Time Patrolmen. They acknowledge that setting the timeline right will result in everyone from the new present day getting erased from existence. But they regard this as a regrettable but necessary sacrifice, and go through with it. Van Sarawak rescues one native of this new timeline (because you Always Save the Girl), and Everard can't bring himself to fully explain to her why she can't go back home.
  • In The Time Ships, the Time Traveller's second trip into the future sends him to a completely different world from the one he remembers. He concludes that with every use of the time machine he is potentially committing murder on an unimaginable scale and vows to prevent himself from ever creating the machine. Later subverted when it turns out that the many worlds model is in effect.

    Live Action TV 
  • Acknowledged and arguably justified in an episode of Buffy, involving not time travel but alternate realities. In the Season Three episode "The Wish", Cordelia wishes that Buffy had never come to Sunnydale, creating an alternate reality in which the town is overrun by vampires. Alt-Giles figures out how to reverse the effect, but at the last second, the demon responsible for it tries to stop him, asking why he thinks the alternate (original) universe is any better than the one he knows. Giles' response? "Because it has to be."
  • This is the main focus of Continuum. The protagonist is thrown back in time with a group of Well Intentioned Extremists who wish to avert the dystopian future. She is faced with the dilemma of either trying to stop them and preserve her future at any cost, or trying to make the future a better place by preventing historical disasters and/or preventing murders. However, there are several added hurdles:
    • The series steadfastly refuses to explain how exactly time travel works, meaning the characters have no idea if they can change the future or not.
    • The protagonist begins the series believing that while her time isn't perfect, it still is worth saving. That is until she is forced to reassess her world and the horrible things that take place there.
    • If the future does change, then her son, husband, and family will be erased from existence.
    • If the future can be changed, then it changed the moment the time travel occurred.
  • Doctor Who:
    • First turns up in "Genesis of the Daleks". The Doctor is given an opportunity (an order, even) to prevent or seriously alter the creation of the Daleks. The only obvious downside is that at that point the Daleks hadn't done anything wrong (yet), and so he'd be committing genocide against a thus-far innocent race, who he knew would turn evil and try to wipe out entire species... he didn't, merely delaying their development for a while, for which causality is thankful
      • And according to fanon, enabling Davros to survive when his creations turned on him. When he was revived later in the original series, he eventually plunged the Daleks into civil war and undercut their threat to the universe for some time.
    • "Father's Day": Rose can't save her father from dying. In this case, it's enforced in part by the Clock Roaches that begin to devour people to "sterilize the wound" caused by the paradox she created.
    • Done beautifully in "The Fires of Pompeii". The Doctor is saddled with the choice of not setting off Vesuvius, thereby saving Pompeii, or sending those people to their deaths in order to keep history intact and to keep the Pyroviles from conquering Earth. Finally, with support from Donna, he sets off the volcano.
    • Comes up again later in "The Waters of Mars", only this time, the Doctor changes history by choosing to intervene.
  • Lost: Several have tried to save the past...and all fail miserably and cause the event, since everything that has or will happen has already happened. Most notably, Daniel's attempts to reset time so that 815 never crashed by stopping the Incident not only results in his death, but probably caused the Incident, since we see Pierre lose his arm, a event referenced in the very first episode with him in it.
  • The Orville: Lost in the 21st century thanks to time travel, Gordon eventually adopts an identity as a pilot and raises a family, despite the risk of a Temporal Paradox. When Captain Mercer finds him and he refuses to return, Mercer takes a drastic measure - travel to a week after the time Gordon "landed" and rescue him, before his children were even born. Alternate past Gordon becomes so furious about the plan, he goes as far as wanting to shoot Mercer.
  • Stargate SG-1 does it in the episode "2010" with Carter's husband wondering if the other timeline will really be better and what happens to them if the plan succeeds. Carter then bluntly tells him that "they" won't exist or exist but in a different way and that the new timeline cannot be worse than the absolutely certain destruction of humanity in less than 200 years. As we know, despite the new enemies appearing later on, she was entirely right.
  • Star Trek: Voyager:
    • Played straight in the episode "Timeless", in which Harry Kim is driven to Set Right What Once Went Wrong, a mistake on his part which killed the crew except for him and Chakotay who were in the Delta Flyer, but both Chakotay and his girlfriend know that this will cause them never to meet. Starfleet also saw it as dangerous and sent LaForge to stop them. This is fully discussed by LaForge himself, who says he completely understands what they are trying to do and would do the same thing in their place, but he has to think of the timeline and his own crew who will be changed by this.
    • Voyager also had a story arc ("Year of Hell", parts 1 and 2) about an an alien Well-Intentioned Extremist who built a weapon that could erase things from history; his intent was to get rid of his species' enemies, but failed to realize that interbreeding with them in the past gave his species an immunity to a specific disease which ended up killing his wife in the altered timeline, leaving him continuously trying to undo the damage by erasing more civilizations. Ironically, even after hundreds of years doing this he never realized what he really needed to erase was the weapon itself. Once Voyager's attack causes it to malfunction and erase itself from history, everything he ever changed returns to normal.
    • Admiral Janeway's plan in the finale "Endgame" is to send Voyager home NOW. Captain Janeway points out that she did get Voyager home after another sixteen years. The plot takes over before they get too philosophical, to the disappointment of many watching.
    • In another Voyager episode, a Negative Space Wedgie splits the ship into various time periods, through which only Chakotay may pass. At the end, Janeway from just before the mission wants to have the ship be restored to her time, thus preventing the ship from being trapped in the Delta Quadrant. Chakotay refuses, claiming that they have helped far too many people in the Delta Quadrant to erase this, as well as the fact that it would add yet another complication into an already-risky solution. (He conveniently neglects to mentions that his own ship would still be trapped in the Delta Quadrant if they follow Past!Janeway's plan.)
      • In the same episode, Seska attempts to do the same thing after realizing that Chakotay's timeline means that he and the others must have taken the ship back from the Kazon. Fortunately, Chakotay and Janeway had anticipated that she might try to backstab them and had a plan in place to stop her.
    • The same thing is proposed by a Past!Romulan commander who ends up communicating with Present!Voyager through a Negative Space Wedgie. He offers to warn Starfleet of Voyager's fate just before the launch, but Janeway refuses. It would have been moot anyway, as Tuvok reveals later that, according to historical data, the commander died long before the Voyager was launched.
  • Star Trek: The Next Generation: Both defied and downplayed in "Tapestry". Picard's artificial heart is damaged and he's about to die, so Q gives him the opportunity to change his past to prevent the injury that led to him getting the transplant. Picard worries that any action he'll take in the past could have disastrous consequences, but Q brushes him off with, "Nothing you do will cause the Federation to collapse or galaxies to explode. To be blunt, you're not that important." But while it doesn't have disastrous consequences for anyone else, the consequences to Picard's own life after not getting in the fight that caused the injury are so bad he immediately asks Q to change it back even if he does die.
  • The Star Trek: Deep Space Nine episode "Children of Time" has the Defiant crash on a world populated by the crew's descendants (and a future Odo), thanks to a time loop. The characters decide they have no choice but to make sure these people live, and prepare to trap themselves in the past. Unfortunately, future Odo couldn't stand to let Kira die again, so he screws with the ship, allowing it to escape and erase the entire colony. Kira doesn't take it well.
  • Discussed in the Star Trek: Strange New Worlds episode "Tomorrow and Tomorrow and Tomorrow". La'an suddenly finds herself in an alternate timeline, and then she and that timeline's version of Kirk go back in time to the point of divergence. Kirk points out that if they succeed in restoring La'an's timeline, his own will be erased, so he doesn't actually have any reason to help her. La'an has to sell him on how much better her timeline is to get him on board, though it is the revelation that his brother is still alive in her timeline that fully convinces him.
  • In the Supernatural episode "The Song Remains the Same", the angel Anna goes back in time to kill John and Mary Winchester before Sam and Dean are born in order to prevent Sam and Dean from kickstarting the Apocalypse. Sam and Dean follow her to save John and Mary but take the opportunity to try to convince Mary to remain childless, as Sam and Dean are willing to cease to exist to stop the Apocalypse. This plan fails because the angel Michael, who is pro-Apocalypse, stops Anna and erases John and Mary's memories of the event.
  • Happens two times in The X-Files:
    • In "Synchrony", a researcher travels from the future to destroy his own research because of the chaos created by practical time travel in his future.
    • Subverted in "Triangle" in which Mulder, as the time traveler, attempts to prevent Nazi agents from stealing "Thor's Hammer," a supposed superweapon aboard a cruise ship. It was All Just a Dream...or was it?

    Video Games 
  • It's implied in a letter from Lucca in Chrono Cross that the main characters of Chrono Trigger have to die as karmic punishment for changing the future. This trope is the springboard for the entire plot of Crimson Echoes.
  • Aversion: Not Time Travel, but worth commenting on; an Ass Pull justification that Marche of Final Fantasy Tactics Advance gives regarding changing Ivalice back into "The Real World" is that surely the Magical Land Ivalice will continue to exist as Another Dimension after he destroys it.
  • Pokémon Mystery Dungeon: Explorers of Time/Darkness/Sky:
    • The game reveals in its final chapter that because you, Grovyle, and Dusknoir all came from the future, the three of you will be erased from the timeline if the Time Gears are returned. The player character gets better.
    • One of the bonus chapters in Sky reveals that even though the Bad Future was prevented, it still exists in some other universe. It gets fixed in this universe too, but thinking about this further can lead to the conclusion that it might still be sticking around in other universes.
  • In Telltale's Back to the Future: The Game, First Citizen Brown (an alternate version of Doc) pulls this on Marty when he discovers that, in Marty's timeline, Brown's wife Edna is a lonely batty mess. It turns out that Marty inadvertently fixes things anyway, as Marty inadvertently fixes up Edna with Kid Tannen, and they end up being moderating influences on each other.
    • There are other sides to Citizen Brown's chastising. Returning everything to Marty's timeline would erase Brown (that is, replace him with Doc Brown from the first two episodes, who has a different personality) and his family and everything in his world. He bitterly concludes that his opinion doesn't matter, because Marty will erase him anyways.
  • Final Fantasy XIII-2: Our heroes Serah and Noel are trying to prevent a bad future in which the human race dies out. The secondary villain, however, believes that they do not exist in any of the timelines which lead to the good future, and tries to sabotage Serah and Noel.
  • The second expansion of Fate/Grand Order, Cosmos in the Lostbelt, has wildly divergent Alternate Timelines competing to replace the entirety of human history. The protagonists are fighting for the original timeline, but they inevitably make friends and allies as they explore each timeline. Unfortunately the mechanics of timelines in this game demand that all of them be erased in order to bring back the original timeline. It's suggested that the protagonists keep seperate from the inhabitants of each one to avoid having to repeatedly face this dilemma, but rejected because of the need to understand what's going on.

    Visual Novels 

  • The second half of Steins;Gate revolves around this. Realizing that the D-Mail experiments he's been conducting help cement a Bad Future and guarantee the death of his childhood friend, Okabe has to negate each one in order to avoid it. The problem? Most of those D-Mails altered the past in ways that granted his friends a good deal of happiness - including his own, as the first D-mail prevented the death of the woman he's fallen in love with.
  • Discussed and averted in Virtue's Last Reward. Although the goal of the AB project is to prevent the release of the Radical-6 virus, the timelines in which Sigma and Phi failed to do so still exist. Phi talks to you about it briefly as part of the Multi-World Interpretation, and Tenmyouji and Quark talk about it during the Golden Ending, and some ethical implications thereof.

  • General Protection Fault had a massive story arc in which the future son of the two main characters went back in time to prevent his Bad Future from occurring, knowing full well (and accepting) the fact that doing so was likely wipe him from existence. It didn't. Probably. That arc was running on weapons-grade Mind Screw towards the end.
  • Briefly addressed in Schlock Mercenary. The cast didn't dwell on it much, probably because their universe was doomed anyway. Though the metaphor used when he makes the jump softens the blow. It also helps that it had only been a few weeks.

    Western Animation 
  • Adventure Time: In "Finn the Human", Jake is in a Place Beyond Time, looking at the disastrous consequence of Finn's wish that the Lich never existed. Prismo can still grant Jake's wish to fix things, but points out how dangerous timeline alteration are, which is so intimidating Jake Stress Vomits.
    Prismo: There's rules to this stuff. Wishing an event to be changes elements before and after it; memories will be destroyed, babies will not be born! Potential worlds could be evaporated. By. Your. Wish.
  • Justice League:
    • "The Savage Time": Defied, as Alternate Batman doesn't like living in an authoritarian regime after the Allies lost World War II and gladly accepts ceasing to be if it means achieving victory.
      Martian Manhunter: You understand that if we do change the past, you — this version of you — will never have existed?
      Alternate Batman: Nothing would make me happier.
    • When Alternate Batman mentions that his parents were killed for opposing the government, he later seems hopeful that they'll have survived if the Justice League changes the past. Superman tactfully mentions that this may not be the case (they don't).
  • Star Trek: The Animated Series: In "Yesteryear", when Spock is erased from the timeline, his role as the first officer of the Enterprise is taken by another figure, an Andorian named Thelen. Restoring the timeline to its undamaged state means also removing him from it. It's not made clear what precisely this entails, but least he accepts his fate bravely and Spock wishes him a long and prosperous life in whatever circumstances he will be placed in. (Like most Trek time travel, it's unclear whether or not he got to stick around in a divergent timeline.)
  • Samurai Jack: It never seems to occur to Jack that, if he succeeds in going back in time and stopping Aku, all the people who he meets and helps in "the future that is Aku" will not exist in the new timeline. This becomes extremely relevant in the last two minutes of the show.
  • South Park: in the After Covid special, adult Cartman refuses to join his friends' plan to go back in time and end the pandemic in 2021 because it'll mean he might never meet his wife and father his three kids (and to a lesser extent, never mature from his bratty, racist past self). In the end, his wife convinces him to go along with the plan, only for him to be proven right - the new good future is better for everyone else, but he ends up homeless.

Alternative Title(s): The Time Travelers Dilemma