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9[[quoteright:350:[[DrosteImage https://static.tvtropes.org/pmwiki/pub/images/ParadoxWomanJ2_931.jpg]]]]
10[[caption-width-right:350:[[WesternAnimation/{{Futurama}} Torn From Tomorrow's Headlines!]]]]
11
12->''"History abhors a paradox."''
13-->-- ''VideoGame/LegacyOfKainSoulReaver2''
14
15A contradiction of causality within the timeline brought about by TimeTravel. Theorized to be [[TimeCrash dangerous to the fabric of reality]], and known to be [[YourHeadAsplode dangerous to the brains]] of anyone who tries to get their head around them. [[BellisariosMaxim So don't]]. It's usually what TheProfessor worries about during a TimeTravel story.
16
17Punishments for creating a paradox vary. You might instantly [[RetGone vanish from history]] or cause your time-travelling self to be [[PuffOfLogic erased]]; you might be immune but find the world around you different; you might [[RealityBreakingParadox destroy reality itself]]; heck, you might even [[ButterflyOfDoom accidentally unleash]] [[ClockRoaches killer flying time monkeys]].
18
19This is all fictional, of course. In reality, a confirmed paradox would disallow time travel to work ''at all''. You see, a logical paradox is not a ''thing'', due to the law of noncontradiction. A paradox is merely a sign in a human-created model that either you have attempted something impossible or that you have incomplete understanding of how something works. Here's the thing: all our notions of causality are based on the fact that time only moves in the one direction and a paradox exploits this cause and effect relationship. Once you throw TimeTravel into the equation and have time move in a different way, it's really anyone's guess what will happen. Not that this prevents authors from abusing the concept as a sort of universe-wide LogicBomb.
20
21There are many kinds of paradoxes that can be created by poorly thought-out time travel, but it usually fits one of these two major categories:
22
23!GrandfatherParadox
24
25This paradox gets its name for a very simple question: "what would happen to you if you went back in time and killed your grandfather before he had offspring?" (Parodied by ''WesternAnimation/{{Futurama}}''; see example in StableTimeLoop)
26
27More generally, this means doing something that '''makes your time travel ''impossible'' or ''unnecessary''.''' For instance, if success in the time travel endeavor means that the condition you [[SetRightWhatOnceWentWrong set out to change]] never happens, then you won't ever have had any reason to come back and try to change it. Thus, without your intervention, it will happen after all, meaning you then must go back to change it, meaning you don't have to, meaning you have to, and so on, ad infinitum.
28
29Most cases of MentalTimeTravel sidestep or ignore the grandfather paradox.
30
31!Ontological Paradox
32
33Also known as the Bootstrap Paradox, this occurs in a StableTimeLoop if you're not ''very careful'' about what you're doing, involving events that are their own causes. While not a paradox in the strictest sense - events remain self-consistent - it does violate normal expectations in surprising ways[[note]]Quantum physics comes into play, see discussion[[/note]]. Common variations include:
34
35!!The Object Loop
36An object from the future is sent into the past, takes TheSlowPath back to the future, and then gets sent back into the past again, in the same way, for the same purpose. For example, you travel to the past and sell a pair of [[Film/StarTrekIVTheVoyageHome antique glasses you got from a friend]], who inherited them from his grandfather, who bought them from you, the time traveler. This time loop results in several important physics problems, such as:
37
38''Where did the glasses come from in the first place?'' The glasses have literally sprung into existence from ''nothing'', appearing to violate the law of conservation of energy/mass. This is sometimes called a "closed timelike curve" in hard SF, and the object itself is sometimes referred to as a "jinn"[[note]]As in the beings mentioned in Literature/TheQuran, not the liquor[[/note]].
39
40''How does the object escape erosion or other forms of damage?'' Since its origin point is also its end point, the object cannot (relative to itself) loop endlessly as it would experience infinite decay (relative to itself) and therefore would not exist to be sent to the past, preventing the loop from occurring at all. Thus, to exist the object must (improbably) escape all forms of damage/erosion/entropy between its arrival and departure; technically, this isn't impossible, but its improbability makes object loops very weird from a quantum mechanics perspective.
41
42In one common variation, ''information'' loops, rather than physical objects: for instance, an engineer from the future gives [[Film/StarTrekIVTheVoyageHome the formula for transparent aluminum to its historical "inventor"]], becoming the creator of a metal that has always existed. This version may avoid the problem of decay, provided that the information is correctly transmitted and recorded. The actual effect of this variation is that no one invented the object, or no one discovered the formula/concept. It's just there.
43
44The object could also be repaired, or otherwise reset to a certain state, at some point during its existence; this would be the closest to creation the object experiences. This is a variant of an information loop, in that the object contains or suggests information (what it should be like) that is used (along with whatever remains of the damaged object) to create the like-new object.
45
46!!The Reverse Grandfather Paradox
47When time travel is involved, cause and effect tend to get muddled. Say you remember being involved in an accident as a child, and would have died if not for the intervention of a mysterious stranger who showed up, saved your life and then vanished without a trace. Later, you become a time traveler and find yourself at the scene of the accident, and there's a little kid who needs saving. That's right: ''you'' happen to be the mysterious rescuer. Instead of accidentally making your time travel unnecessary or impossible by meddling with the past, your meddling somehow made it required or possible in the first place. But then the question becomes how you ''originally'' (an increasingly meaningless concept in this context) survived to time-travel and save yourself.
48
49Thus, an ontological paradox occurs, which is not actually a paradox in the logical sense, but a confusing and counter-intuitive result of time travel. This also precludes a multiverse explanation, since both child and rescuer-adult occupy the same timeline and universe, if the child has a childhood-memory of being rescued by the adult-self.
50
51Normally, as written, the temporal paradox never turns out to be as dangerous as TheProfessor imagined it would be, or it turns out the characters were [[StableTimeLoop "supposed to do it"]] [[YouAlreadyChangedThePast in the original timeline]]. The latter ontological paradox is also known as a predestination paradox, and the resultant philosophical questions are rarely thought about in the series.
52
53If two time periods are featured, the effects of a paradox will usually be visible in the future only "after" the cause has happened in the past (see MeanwhileInTheFuture).
54
55Interestingly, series rarely [[TimeyWimeyBall have the same result to paradoxes even in the same show.]]
56
57The most common effect of a paradox, on TV at least, is to trigger the ResetButton and unmake the entire episode's consequences.
58
59Theoretically, a paradox that consists of two mutually-exclusive events can have one of two results: either the fabric of reality rips itself apart trying to determine which reality is the 'correct' one, or -- according to Multiverse Theory -- it's discovered that causing a paradox is a technical impossibility, as each supposed 'paradox' merely creates two 'alternate' timelines -- one for 'Situation A' and another for 'Situation B'.
60
61(Of course, Multiverse Theory also holds that time-travel is ''hypothetically'' possible -- since every choice made, and every action taken, and every word ever written, creates a series of 'alternate universes', each being slightly different to account for the results of the choice/action/word, we would just need a consistent way to travel 'between' the various 'multiverses' thus created.) On the flip side, it also means that it's impossible to ''completely'' SetRightWhatOnceWentWrong, as the "original" timeline will always be unchanged.
62
63The [[https://www.newscientist.com/article/2227304-time-travel-without-paradoxes-is-possible-with-many-parallel-timelines/ current thinking]] is that time has a built-in paradox buffer: essentially, having to go backwards in time forces the traveler into another dimension, meaning if they kill their grandfather, they didn't kill ''their'' grandfather -- they killed their counterpart's grandfather, meaning their counterpart will never be born. (It also means that going into the past, you're stuck in whatever dimension you've happened to travel to.)
64
65Compare TimeyWimeyBall, StableTimeLoop. If time is somehow dangerous besides from paradox, it's TimeIsDangerous.
66
67----
68!!Example subpages:
69[[index]]
70* TemporalParadox/AnimeAndManga
71* TemporalParadox/{{Literature}}
72* TemporalParadox/LiveActionTV
73* TemporalParadox/VideoGames
74* TemporalParadox/WesternAnimation
75[[/index]]
76
77!!Grandfather Paradox examples:
78
79[[foldercontrol]]
80
81[[folder:Comic Books]]
82* Creator/GrantMorrison's legendarily complex and metafictional series ''ComicBook/TheInvisibles'' hinges itself on contradiction, and details several brainbending temporal paradoxes. It would perhaps be remiss to go into any of them here in any great detail. Basically, if you like that sort of thing, go read ''The Invisibles''.
83* The Franchise/MarvelUniverse has a simple solution for this in the novel trilogy ''Time's Arrow''. There are a large--but not ''infinite''--number of alternate universes, that deal with what ifs. If someone in those timelines goes back in time to change something, it will create a new timeline that's an offshoot of one's own from that point. No going back and killing Hitler, Cyclops notes when told this--the idea being that if you do so, your ''own'' timeline will be unaffected. Oddly, this doesn't seem to be the case in the comic universe.
84** Except when it is that way. You don't think that any two comic writers actually agree on how this stuff works, do you? That said, the ''ComicBook/EarthX'' series (including Universe X and Paradise X) suggests a couple of different versions of this. In the end, it is fundamentally, philosophically important that the idea that [[spoiler:alternate universes branch off only as a result of time travel]] is true.
85*** This is generally accepted; however, it has been shown that Doctor Doom has invented technology that allows this rule to be broken in PAD's ComicBook/XFactor run.
86** This is the reason time traveling villain Kang the Conqueror keeps [[MesACrowd multiplying,]] often despite his own wishes.
87** One run of ''ComicBook/{{Thunderbolts}}'' ended with the present-Thunderbolts meeting the past versions of themselves. Fixer killed his own past self, and the universe promptly began collapsing. [[spoiler: Fixer resolved it by having himself de-aged and his memories erased, in order to replace himself in the past. He thereby condemned himself to live in an infinite loop, reliving the same period of time over and over for eternity.]]
88** One exception, however, are the Space Phantoms, servants of time-traveling ''ComicBook/TheAvengers'' villain Immortus, who learned the hard way how dangerous this sort of thing is. Apparently, the Phantoms learned time travel before they learned space travel, and when a civil war broke out between them, each side tried using time travel to change the outcomes of important battles. If a side did so successfully, the other side would try to undo it, again and again, until finally, the constant meddling with the temporal flow destroyed their world, leaving them a DyingRace trapped in the dimension of Limbo who are little more than slaves to Immortus' will.
89* ''ComicBook/MightyMorphinPowerRangersShatteredGrid'' has a very ''painful'' one. [[spoiler:In the very first part, [[BigBad Lord Drakkon]] [[TheHeroDies kills Tommy Oliver]] to recharge the Green Crystal. However, since Tommy is massively integral to the Power Rangers timeline (as he would become the White Ranger, Red Zeo Ranger, first Red Turbo Ranger and the Black Dino Thunder Ranger), the Morphin' Grid decides to fix this little problem by dividing ''every Ranger era'' into its own separate universe just to prevent this.]]
90* ''ComicBook/{{Shakara}}'': The fellow members of The Hierarchy that the Overlord was planning on betraying go back in time to stop him before he can carry out his plan. He compliments their ingenuity but mocks their attempt, pointing out that this would only create a temporal paradox that would result in an alternate timeline, it wouldn't stop what they've already seen him do in the future. However, even that rests on the assumption that [[CurbStompBattle he could be killed to begin with]].
91[[/folder]]
92
93[[folder:Fan Works]]
94* In the ''Fanfic/FacingTheFutureSeries'', Sam decides to try getting ghost powers for herself when she discovers that her future self just so happens to have ghost powers just like Danny does.
95[[/folder]]
96
97[[folder:Film -- Animated]]
98* ''WesternAnimation/MeetTheRobinsons''. Let's see. If Goob made the catch and won, getting himself adopted and never becoming [[spoiler:the Bowler Hat Guy]], Lewis would never have learned that Goob became that person, and never bothered to prevent it. Yeah. And he wouldn't know not to create Doris.
99* ''WesternAnimation/TheUltimateEnemy'' is one big temporal paradox. In the original timeline, WesternAnimation/{{Danny|Phantom}}'s family and friends are killed, he goes mad with grief and kills himself (people with a SplitPersonality can do that and survive), and his [[SuperpoweredEvilSide evil self]] terrorizes the world for ten years. Thanks to Danny and some timely interference by the DungeonMaster, this timeline was erased, but his evil self was in the past when it was erased, so he still exists even with the events that caused his existence never happening. His evil self even pointed out the paradox. "You don't get it, do you? I'm still here. ''I'' still exist. That means ''you'' still turn into me." The Observants mention something about him still being there because "he exists outside of time."
100[[/folder]]
101
102[[folder:Film -- Live-Action]]
103* In the ''Franchise/BackToTheFuture'' movies, Doc Brown is very concerned with temporal paradoxes.
104** However, the effects of time travel are ''different'' in the various movies. For instance: in the first movie, Marty's accidental stopping his parents getting together was starting to delete him from existence; in the second movie, Biff interferes with his past, and the changed present has Biff saying he sent Marty to a school in Switzerland, yet this never affects the time-travelling Marty.
105** {{Fanon}} has {{justified|Trope}} this in various ways; for example, saying the time traveller is only affected by his own changes to the timeline, or by saying that he will be unaffected as long as there's somewhere in the timeline for him to "slot in" - changes to his situation in the new timeline are shrugged off, as long as he exists ''somewhere''.
106** The documentaries on the DVD set mention how the justification was that there's some entity that regulates time itself. The partial deletion over time of Marty, why both Jennifers fainted when they met each other, and why even with relatively major changes to the timeline, Marty's family, home, and association with Doc Brown and Jennifer remain largely the same. They wanted to explore this aspect, but couldn't find a way to incorporate it into the films without it being obtrusive. [[Website/{{Wikipedia}} The Other Wiki]] has more information [[http://en.wikipedia.org/wiki/Back_to_the_Future_timeline#Time_Travel_Theory here]].
107*** One possibility is that there are two Martys, just as there were in 2015 and when he returned to 1955.
108** Much stranger is how Biff, when he returned to 2015, returns to the version where he is a loser, instead of the one where he is rich. The only clear reason for this was so that Marty and Doc could get the [=DeLorean=] back.
109* The whole plot of the movie ''Film/TheButterflyEffect'' revolves around the main character's ability to travel back in time and change parts of his life. Every change causes [[spoiler:his brain to physically rewire itself with the new memories, though, and this causes intense pain for him.]]
110* ''Film/DonnieDarko'': After sleepwalking away from the place where he was supposed to die, the eponymous character is caught in an unstable time loop that he must close. [[spoiler:When he moves himself and the jet engine that should have killed him back into the past, he closes the loop by dying in the way that he should have from the beginning, negating everything in the time loop.]] This causes everything that was changed by his time travel to exist outside of the normal timeline without affecting it. [[GainaxEnding Maybe.]] It's pointed out in the movie, more explicitly in the extended cut, that the cause of the time loop only happened because of the time loop; in the final timeline [[spoiler: the jet engine falls into the past and kills him for no reason whatsoever. In-universe speculation is that a deity or other being outside time caused it for reasons of their own]].
111* ''Film/{{Frequency}}'' depicts basically the same situation as ''The Lake House''--[[SpaceIsMagic due to abnormal sunspot activity]], a police officer and his long-deceased father are able to communicate across a 30-year gulf of time over the same CB radio set. [[spoiler:The son first saves his father from dying in a firefighting mishap, only to discover that he died of lung cancer a few years later anyway. But he then manages to convince him to quit smoking.]]
112* ''Film/{{Interstellar}}'' features a semi-temporal paradox, baring a similarity to the Reverse Grandfather Paradox. All of the scenarios in the Paradox are initiated by [[spoiler:Cooper and TARS manipulating space-time inside the Tesseract.]]
113* ''Film/TheLakeHouse'' is a story about a mailbox that delivers letters from Kate to Alex ''two years ago'' and vice versa. [[spoiler:Alex dies in a car accident on Valentines Day. Two years later, when Kate realizes that, she sends a message to Alex two years ago telling him not to be there, and he survives.]] It should be noted that the Korean movie this movie is based on dealt with the paradox differently: [[spoiler:The female character sends the warning back in time, but the male character remains dead. Meanwhile, the insertion of the warning splits off an alternate universe where the male character survives, and the movie ends with the male character meeting the female character, just as the female character is moving into the house, before she's even gotten the first letter. It's okay, though. The guy has quite a story to tell her. Since the movie ends there, by the way, it's unknown whether the female character would have ever started the letter-exchanging if the guy hadn't...ugh, it's all sort of vague, really.]]
114* Pretty much every film in the ''Franchise/PlanetOfTheApes'' franchise.
115* Averted in ''Film/TheTimeMachine2002'', where the time traveler attempts to save his fiancee, but she always dies on the same night no matter what he does. He travels into the future to find out why. [[spoiler:In the far, far future, he learns from a more evolved human that if he saved her he would not have the motivation to build his time machine. Apparently, a paradox is allowed if it doesn't prevent the time travel device's creation, though.]]
116* The horror film ''Film/{{Triangle}}'' has loads upon loads. How it works, nobody knows, as even WebVideo/{{Phelous}} can tell you.
117* In ''Film/{{Wishmaster}}'', the main character gets one wish from the evil djinn, after which it will be freed to work its evil upon the world unfettered. She wishes that a particular forklift operator had not been drinking on the job a few days before. Since he wasn't drinking on the job, he didn't drop a particular crate. Since he didn't drop the crate, the statue inside never broke. Since the statue never broke, the gem inside was never uncovered. And since the gem inside was never uncovered, the djinn trapped inside it was never released. But wait! Since the djinn inside it was never released, that means he never granted the protagonist's wish! And if he never granted the wish, then he was released after all! [[LogicBomb But then...]]
118[[/folder]]
119
120[[folder:Scripts]]
121* In ''Script/{{Watchmen}}'', Dr. Manhattan goes back in time and [[GrandfatherParadox prevents his own accidental creation]], ultimately negating the film's entire timeline.
122[[/folder]]
123
124[[folder:Tabletop Games]]
125* The German RPG ''TabletopGame/TheDarkEye'' takes a similar approach in declaring time a dynamic, "healing" weave. An example to solve the grandfather paradox is to have the person get stranded in time, get a life, meet a woman, marry and have kids and thus becoming his own grandfather.
126* In the RPG ''TabletopGame/FengShui'' there are no temporal paradoxes, because history rewrites itself to accommodate changes in the timeline. For instance, if Donald Fong goes back in time and kills his great-great-grandfather, when he returns to the present, he'll find that everyone now knows him as Donald ''Wong'', a person with a very similar life to Donald Fong. He'll remember his old life as Donald Fong, but everyone else will always have known him as Donald Wong. In extreme cases - such as when someone controls enough feng shui sites to cause a critical shift (i.e. they change reality) - people can get written out of the timeline entirely; they still exist, but they have no past in the current timeline, because their version of history simply doesn't exist anymore.
127[[/folder]]
128
129[[folder:Visual Novels]]
130* The actual ''objective'' of Servant Archer[[spoiler:/Heroic Spirit Emiya]] in ''VisualNovel/FateStayNight''. [[spoiler:He tries to kill his younger self (the protagonist, Emiya Shirou) to force a contradiction within Gaia, which he hopes will cause his whole existence to be erased to keep reality from breaking from the impossibility of the event. He himself admits that this would have a very low chance of happening, considering that by meeting Archer, Shirou is already set on ''not'' becoming Heroic Spirit Emiya, so the death of a "different" Emiya Shirou shouldn't affect Heroic Spirit Emiya in the slightest.]]
131** Besides, [[spoiler:it's said that the Heroic Spirits are removed from the time axis and await their summonings in the Seat of Heroic Spirits. So, even in the case that Shirou actually ''did'' want to become a Heroic Spirit, as Archer is no longer bound by the rules of time, Shirou's death would not form a paradox and free him from his destiny. Archer's whole objective in UBW was both to attempt this plan anyway in the off-chance that it actually succeeded, and to make sure his past self didn't have to see his ideals betray him like he did.]]
132* ''VisualNovel/{{Infinity}}'':
133** At one point, ''VisualNovel/Ever17'' features a time-travel attempt to SetRightWhatOnceWentWrong with an obvious fix. Unfortunately, this also undoes the events that triggered the attempt, resulting in [[https://static.tvtropes.org/pmwiki/pub/images/ever17_time_paradox.jpg a very unpleasant paradox]]. Warning. That link is hellishly disturbing.
134** In several Bad Ends of ''VisualNovel/Remember11'', death of one of the main characters causes the story's StableTimeLoop to shatter, leading to them [[{{Retcon}} discovering themselves sometime before the exchanges started]] -- [[spoiler:[[DyingDream freezing to death in the plane's wreck]]]] for Kokoro, and [[spoiler:[[CuckooNest stuck in an asylum as "Enomoto"]]]] for Satoru.
135[[/folder]]
136
137[[folder:Webcomics]]
138* [[spoiler:Chuck Goodrich]] of ''Webcomic/TheAdventuresOfDrMcNinja'' traveled back from the future to stop a ZombieApocalypse. Then ''another'' of him showed up in order to stop a RobotUprising. And then more and more.
139* In ''Webcomic/AmericanBarbarian'', [[http://www.ambarb.com/?p=417 Rick refuses to do anything that would prevent their births]].
140* ''Webcomic/FaultyLogic'': Fox built a time machine for the sole purpose of traveling back in time to prevent himself from building a time machine, because he knew he would build a time machine and misuse it.
141* In ''Webcomic/{{Homestuck}}'', most of the technology that can teleport an object thorough time and space are designed to prevent these paradoxes; appearifying an object that would cause a paradox instead creates a copy made of paradox ghost slime, which quickly collapses in a puddle of goo. It ''is'' possible to cause a grandfather paradox, but this creates a doomed AlternateTimeline marked for deletion - even if someone travels back to the main timeline somehow, they're still doomed to die.
142** [[spoiler:Except for Davesprite, who seems to have dodged Fate's bullet by merging with a pre-existing entity in the main timeline, i.e. the kernelsprite.]]
143* In the ''Webcomic/{{Oglaf}}'' strip "Chronotherapy", a healer goes back in time to cure a plague before it devastates the kingdom, then goes to the queen to claim the StandardHeroReward she promised him. Since the plague never happened, the queen never hired him, so she doesn't know what he's talking about.
144* The high cost to reality is invoked and elegantly resolved in [[http://www.penny-arcade.com/comic/2004/05/03/ this]] ''Webcomic/PennyArcade'' strip.
145* ''Webcomic/SchlockMercenary'':
146** Paradox is notably averted in every instance of time travel, where it's put forth that causality is ''never'' sacrificed. If a time traveler were to go back and kill his/her grandfather, even though another one of them wouldn't be born as a result, they've already caused the event, so they'll still exist. Changes due to time travel are likened to "overwriting" the original timeline (though it's also worth mentioning that, within the Schlockiverse, time travel is normally impossible).
147** The comic itself likens it to the most common time travel power in video games: [[SaveScumming "Load Game"]].
148** And in the storyline where the figured out that time would keep going: Petey and Kevyn ended up with two copies of a VDA probe, in the process of trying to figure out if they could change the past. (Short reason why- they wanted to prevent the activation of a device that was currently in the process of destroying the Galaxy.) Kevyn ends up shooting the version of the probe that hadn't been sent ''yet'', arguing that even if they repair it, it wouldn't be identical enough to cause the "identity crisis" in the onboard AI that caused them to discover the duplication to begin with, thereby showing that "the future" could be change, without voiding their personal past. So, go ahead and send someone back far enough, make the change, and don't worry about disappearing in a puff of logic.
149--->'''Petey:''' Okay, confession time... when you fired, I was genuinely frightened for the first time in this whole affair.\
150'''Kevyn:''' You call that a confession? Here's a real confession: So was I. But hey, now we know it works, right?
151* Evil Katarakis of ''[[Webcomic/{{Starslip}} Starslip Crisis]]'' hasn't thought his brilliant plan all the way through:
152-->Imagine... enjoying your favourite '''''sandwich'''''... then going back and stealing the sandwich from yourself '''''before you eat it! So you get two sandwiches.'''''
153** [[TimeCops Deep Time]] isn't exactly the best off, either: one member spent spare weekends going back in time to kill Hitler, then back again to stop himself from killing Hitler. Another spends forty years on dead-end research, then tells a third agent to stop him from wasting his life on the matter. In yet another case, accidentally blowing up a planet causes an entire Deep Time spaceship to spontaneously fall apart.
154*** At one point, people in the present protect themselves against attackers from the future by identifying the future guys' ancestors, and making sure they're on all the ships that the future guys are attacking.
155[[/folder]]
156
157[[folder:Web Videos]]
158* ''WebVideo/NightmareTime'': In the episode "Killer Track", Miss Holloway is approached by Rose to help remove a curse that she received by listening to the titular Killer Track. Miss Holloway travels back in time to possess Rose's body, making it so that she was the one who heard the song, not Rose.
159[[/folder]]
160
161!!Ontological Paradox examples:
162
163[[folder:Comic Books]]
164* In ''ComicBook/AllNewAllDifferentAvengers'', the team makes sure to prevent this: [[spoiler:Kang ends up knocking the Sam Wilson Captain America and Jane Foster Thor three days into the future, making sure that Thor lost the hammer. Cap gets Jane back to the hammer where it fell three days prior and use it to return to the present, then proceed to ''weaponize'' Temporal Paradox to drive Kang out. At Iron Man's suggestion, Thor drops the present day hammer in a spot so that she can find it once more without construction crews finding it and trying (and failing) to move it]].
165* ComicBook/BoosterGold only becomes Booster Gold because as Michael Carter, a janitor in a 25th-century superhero museum, he steals a timesphere belonging to the time master Rip Hunter. It later transpires that [[spoiler:Booster will father Rip Hunter and teach him everything he knows about time travel]]. So if he hadn't stolen the timesphere, the timesphere wouldn't have been there to steal in the first place. Augh. To complicate matters, [[spoiler:Rip has to train Booster to be a time master so that Booster can have trained ''him'' to be one when he was a little boy.]]
166* In Pre-Crisis Franchise/{{Superman}} comics, all time travel works this way, which is why Superman's ability to time travel by exceeding the speed of light is not a GameBreaker; he can travel back to the past, but he can't successfully change anything. TheMovie ignores this.
167[[/folder]]
168
169[[folder:Comic Strips]]
170* Unsuccessfully {{invoked|Trope}} and thereby {{subverted|Trope}} in ''ComicStrip/CalvinAndHobbes'': Calvin tries to travel two hours into the future so that he won't have to write the story they're supposed to be writing for school. But the future Calvin doesn't have it, because he was to busy time travelling to the future to actually write it. Then they both travel to one hour ago because they decide that that Calvin should have written it... but he refuses on the grounds that whatever they threaten to do to him, they'll be doing it to themselves. In the end, the two Calvins return to the future empty-handed, only two find that the two Hobbeses have written the story for them. When Calvin starts reading it out loud at school, it turns out to be a story about [[spoiler:his foolish time-travel while the tiger(s) save(s) the day]].\
171The timeline of this whole thing is a little paradoxical, but at least the object/information obtained has an origin.
172[[/folder]]
173
174[[folder:Fan Works]]
175* ''Fanfic/EggmanGenerations'' has Eggman consider this when his younger self, as per the ending of Sonic Generations, consider going into teaching rather than world conquest. Despite this, Eggman notes that the decision hasn't affected his own existence.
176* Link saving himself in ''[[FanficRecs/TheLegendOfZelda The Legend Of Zelda: The Return]]''.
177[[/folder]]
178
179[[folder:Film]]
180* In ''Film/BackToTheFuture1'', Chuck Berry steals "Johnny B. Goode" from Marty (after hearing an incomplete performance over a 1950s payphone, no less), who learnt it from Berry in the first place.
181* Referenced in ''Film/DejaVu2006'' by agent Carlin right before they send a note back in time:
182-->'''Technician:''' It would have gone faster if you had written it [the note] yourself.\
183'''Carlin:''' Yeah, then I recognize my own handwriting and the universe explodes.
184* In ''Film/MinorityReport'', Precogs can predict murders before they happen (hours for crimes of passion, days when premeditated). The protagonist finds himself being accused of a premeditated murder of a man he has never met. He naturally assumes himself to have been framed. To this end, he studies the visions of the Precogs to track down this individual. It is these acts which make the murder premeditated, since he's actively trying to find this guy and will supposedly end up killing him. [[spoiler:This leads to the FridgeLogic problem with the entire movie: how the hell could Burgess have arranged such a thing? The last time he used the Precogs to do such a thing, he did it in a wholly logical way. His framing of Anderton is wholly illogical, since there's no apparent source for the vision and no way it could have happened naturally. The setup is entirely dependent on events that never would have come to pass without Anderton having been present to see the precogs' vision; their prediction itself is the very cause of what they predicted.]]
185** [[spoiler:The precogs, or more accurately Agatha, the skilled one, might have constructed the vision themselves, in order to bring about the events of the movie and end their torture: dreaming of nothing but murder all the time.]]
186* ''Film/{{Predestination}}'', being an adaptation of the below-mentioned ''Literature/AllYouZombies'', has the temporal police protagonist [[spoiler: being his/her own father/mother/recruiter, and the very person s/he is hunting, as s/he sleeps with his/her future self, has a baby who is abducted, ends up meeting his/her recruiter at a bar to join the temporal police, runs into his/her past self on a mission, impregnates her/him with... her/himself, who is taken from her/him after birth and left at an orphanage, then goes to hunt the so called 'Fizzle Bomber', only to eventually find that said criminal is his/her future self, having gone mad.]]
187* Another Creator/SandraBullock film, ''Film/{{Premonition}}'', [[PlayingWithATrope mixes this trope]] with YouCantFightFate: [[spoiler:Linda's attempts to prevent her husband's death cause it, but she does get pregnant before he dies, and prevents herself from going crazy and getting committed,]] which she could not have done had she not had the premonitions of the future.
188* ''Film/StarTrekIVTheVoyageHome'':
189** An Object Loop gets {{lampshade|Hanging}}d when Kirk pawns his reading glasses in 20th Century San Francisco.
190--->'''Spock:''' Excuse me, Admiral. But weren't those a birthday gift from Dr. [=McCoy=]?\
191'''Kirk:''' And they will be again. That's the beauty of it.
192*** Except there's no reason to think there IS an Object Loop occurring, other than Kirk's offhand comment, since the glasses he sold could have easily simply been lost and destroyed over time while the version that existed at that time continued on into the future to become the pair that Kirk sold in the past.
193** There's also an Information Loop, in the form of Scotty providing the formula for "transparent aluminum" to a 20th century scientist, who, it is implied, will go on to "invent" it. The novelization explicitly states that the scientist they give the secret to IS the historical inventor of transparent aluminum, which was only the beginning of his accomplishments, and Scotty observes that it might be ESSENTIAL that they give it to him. In the film it's merely hinted at: [=McCoy=] complains about giving the scientist the formula and Scotty replies "How do ''we'' know he wasnae the one who ''invented'' it?"
194* ''[[http://www.imdb.com/title/tt0498567/ Summer Time Machine Blues]]'' is a Japanese film that starts with a group of high school students on a hot summer day stumbling upon a time machine and using it to prevent the remote control for their air conditioner from fizzling out due to a spilled coke can. ''HilarityEnsues''.
195* ''Film/TheTerminator'': Fathering the guy who will send you back in time counts, too. Also, where did the message about how "the future is not set" originate? Chronologically, Kyle first gave it to Sarah in 1984 as a message Future-John had sent with him when he sent him back in time. Then Sarah decides to teach it to present-John when he is a child so that he will have the message to send. So she gives the message to John, who gives it to Kyle, who goes back in time and gives it to her, who gives it to John, who gives it to Kyle, who goes back in time and gives it to her, who oh look I've gone cross-eyed.
196* ''Film/{{Timecrimes}}'' could have been renamed ''Ontological Paradox: TheMovie''. The protagonist travels backwards in time, and ultimately ends up responsible for the events that caused him to travel back in time.
197* In ''Film/TheTimeMachine2002'', the uber-Morlock explains, "You built your time machine because of Emma's death. If she had lived it would never have existed, so how could you use your time machine to go back and save her?"
198* ''Film/{{Willow}}'' contains a predestination paradox (if you assume, as the film does, that prophecy really is knowledge of the future): Bavmorda's attempts to destroy Elora are the very thing that causes her own destruction, which she would not have attempted to do EXCEPT for foreknowledge that Elora was going to cause her destruction.
199[[/folder]]
200
201[[folder:Video Games]]
202* In a side story "Two Knights and the Holy Sword" from ''VideoGame/AnotherEden'', [[spoiler: Deirdre's sword was given to her by herself from the future, who only had it because her past self had it.]] This creates an object loop where an item only exisits because of time travel.
203* ''VideoGame/BlazBlue'': Ragna the Bloodedge calls himself that because his {{BFS}} and BadassLongcoat used to belong to a hero named Bloodedge, and he wanted to honor the name of that hero. [[spoiler:Said hero is, of course, a time-displaced Ragna with amnesia. Which means the sword and coat just keep getting sent back in time with him and then given to him again by Jubei.[[note]]Whose name is actually Mitsuyoshi, by the way. Bloodedge could never get his name right and [[AmnesiaMissedASpot kept calling him Jubei for some reason]]. After Bloodedge's death, he decided to adopt the name permanently in his friend's honor, and then eventually met Ragna...[[/note]]]]
204[[/folder]]
205
206[[folder:Visual Novels]]
207* ''VisualNovel/{{Infinity}}'': Ubiquitous in the series:
208** ''VisualNovel/Ever17'': Information Loop in [[spoiler:Blickwinkel telling You'haru the plan to save Takeshi and Koko, and You'haru explaining ''him'' the plan 17 years later.]]
209** ''VisualNovel/Remember11'': Both Information Loop and Object Loop with Yuni's terabyte disk, which travels endlessly between 2011 and 2012 and back. [[EpilepticTrees Possibly]] Reverse Grandfather Paradox in [[spoiler:"player's" involvement in the story, as "it" corrupts Sayaka, causing Satoru to devise a plan to summon and send it back in time, making "it" corrupt Sayaka...]]
210* ''VisualNovel/ZeroEscape'':
211** ''VisualNovel/VirtuesLastReward'': [[spoiler:Dio planted four bombs throughout the facility. You only manage to get three of the disarm codes out of him in three different timelines, while the fourth is told to you by Zero Sr. in a recorded message in a fourth timeline. Problem is, you ''are'' Zero Sr. Or rather, he's your future self, meaning he only knew the code because he watched that message back when he was you, meaning the code seemingly came from nowhere. This one at least got explained by WordOfGod: Zero Sr. just had Akane hack that particular bomb and change its code to the one from the message, since he didn't know the real one]].
212** ''VisualNovel/ZeroTimeDilemma'': [[spoiler:Phi is in possession of a brooch that was passed onto her by her unknown mother. In one timeline, Phi burns to death in the incinerator, after which only her brooch is left. Afterwards, Sigma and Diana are trapped in the nuclear bomb shelter for 10 months, leading to the two of them hooking up and Diana giving birth to twins: a girl and a boy whom they name Phi and Delta respectively. She and Sigma then use the Transporter to send the twins back in time to the year 1904, as they do not have any food remaining in the shelter. Diana puts the Brooch she got from the incinerated Phi into the Transporter with the infant Phi. In 1904, the German scientists studying the Transporter then send Phi forward to the year 2008. However, the Transporter only makes copies of whatever is sent through it while the originals stay where/when they are. 1904!Phi lives for 120 years, gets a job at the American facility that bought the Transporter from the Germans, adopts and raises 2008!Phi when she finally comes out of the machine, and passes the brooch down to her. This seemingly creates an ontological paradox: Diana received the brooch from the incinerated Phi, after which Diana sends the brooch back in time to 1904 with Phi, who then passes the brooch on to 2008!Phi who then gets incinerated in ''ZTD'', and Diana sends the brooch back again. Why the brooch doesn't degrade after being incinerated, sent back in time and then existing for 100 more years an infinite number of times is unknown, but that is generally a problem with ontological paradoxes, as they practically don't have an origin. And technically, most things that happen in ''Zero Escape'' are an ontological paradox.]]
213[[/folder]]
214
215[[folder:Webcomics]]
216* In ''Webcomic/EightBitTheater'', [[http://www.nuklearpower.com/2005/03/26/episode-532-20-power-loaders-vs-20-alien-queens/ Thief comes up with a plan by watching a future Red Mage carry it out.]] Red Mage immediately wonders about the paradoxical implications.
217** Later, [[http://www.nuklearpower.com/2006/01/21/episode-651-thief-of-time/ Thief steals his class change from his future self]], only to later lose it when [[http://www.nuklearpower.com/2009/09/19/episode-1174-oh-thats-what/ his past self steals it from him]]. This class change has no origin.
218** Red Mage also accuses [[spoiler:Chaos]] of having an unworkable plan because of a variant on this. [[spoiler:Chaos intends to destroy all of space and time which would destroy all the events leading up to his being summoned to destroy all of space and time]]. (Reaction: [[spoiler: I'd better not create a temporal paradox! I'd hate it if everything were destroyed the way I wanted it to be destroyed!]])
219* At the climax of the Doc Gets Rad chapter of ''Webcomic/TheAdventuresOfDrMcNinja'', villain [[spoiler:Sparklelord]] is sent back in time to the moment when he originally entered from AnotherDimension. This version apparently overwrites the original copy of him, but without any accumulated memories, thus condemning him to repeat the same sequence of events for eternity. So there is an infinite quantity of him entering the loop, but nothing coming out... huh? Presumably, the only reason the universe doesn't implode is that the comic runs on the RuleOfCool.
220* From ''Webcomic/BobAndGeorge'', [[http://www.bobandgeorge.com/archives/010619c this]] ontological paradox shows the time-traveling X and Bass giving Dr. Light and Dr. Wily the ideas to create them in the first place.
221* In ''Webcomic/{{Educomix}}'', two objects--Jessica's mask and Dave's fez--literally come from nowhere, having been given to their original owners by people from the future. [[spoiler:This causes a "Time Fart", which drains energy from other universes to keep the paradox in place.]]
222* In [[http://faultylogic.comicgenesis.com/d/20071006.html this]] ''Webcomic/FaultyLogic'' comic the main character builds a time machine to steal ideas for comics from his future self, only to have them stolen by his past self several seconds later. In essence, these ideas only exist for several seconds, over and over again.
223* Fairly early in ''Webcomic/GunnerkriggCourt'', protagonist Annie is saved from death by a robotic bird creature, which she later describes in detail to her best friend Kat. Kat is intrigued by this and spends years trying to construct something similar. Much later, Kat sends her creation back in time to save Annie's life. Kat herself points out that this situation is impossible since she got the idea from Annie not dying in the first place.
224* ''Webcomic/{{Homestuck}}'' contains probably the mother of all ontological paradoxes: [[spoiler: The Heroes create their parents from their own genetic material, and then create themselves from their parents material, then send the parents and children back in time to become themselves.]] There's even a term for this: Paradox Cloning, when a person is cloned from themself.
225** It should be noted that those examples happen all the time. Locally to John's session [[spoiler: a group of previous players make contact because one of the players, Terezi, found money that was sent to her on her orders. They only look for this money because later John and his group will send an omnipotent demon into the previous playing session. This previous group of players, once aware of the humans, use internet messaging to talk to them all over the course of their lives, usually in heavily non-linear fashions that create stable time loops either way.]]
226*** Worth noting that Terezi told Dave to wire her past self money so that she would discover him and be able to tell him to wire her the money.
227** For a more minor example, at one point Jade complains to John that [[RunningGag her pumpkins keep disappearing]] so John sends her some pumpkin seeds for her birthday. However, these get sent back in time, and it is receiving that present that inspires Jade to start gardening in the first place.
228** For another, we have one of John's conversations with Karkat, who is trolling him backwards through time. Karkat claims that John told him that humans hatch as slugs instead of being born, and John tells him that's completely false but thanks him for the pranking idea. Sure enough, in John's next conversation with Karkat, he tells him exactly that and Karkat believes him.
229** For ''another'', much later on Karkat opens a memo only to be distracted by himself from ten minutes into the future angrily responding to it. Throughout the course of this conversation present Karkat becomes [[HairTriggerTemper characteristically enraged]] and when it's over goes to take it out on himself from ten minutes ago, starting it all over again. Future Karkat even lampshades this, stating that the whole bad mood basically sprung from nowhere and wondering whether it's even real. Yeah, Homestuck likes to play around with time a ''lot''.
230** There's even a whole class of artifact whose defining feature is being an ontological paradox. A juju is a supernatural artifact whose origin is impossible to trace specifically because it exists in a StableTimeLoop. One in-universe theory supposes that they are spontaneously created ''ex nihilio'' by Paradox Space. [[spoiler:Lil' Cal is a juju, one whose Stable Time Loop encompasses at least three separate universes.]]
231* Trying to understand a complicated series of events in ''Webcomic/IrregularWebcomic'' seems to lead to this conclusion. Two characters are captured for OrganTheft purposes. Their future selves come to save them, but end up being captured as well. The original pair having their organs stolen survive by stealing the organs from their future selves, but eventually come across their original organs, and put those in them as well so that when their organs are stolen, only the spares are taken. [[http://irregularwebcomic.net/1871.html It's all very complicated]]. Of course [[spoiler: the characters end playing a part in destroying the universe by destroying the only time machine in existence instead of using it to become their future selves.]]
232* In ''Webcomic/{{Jack|DavidHopkins}}'', [[spoiler: Drip]] unwittingly gets a chance at one, but he blows it and closes a StableTimeLoop instead. [[spoiler: The Devil offers to trade Drip the scarf his mother wore in life in exchange for the murder of a married couple. Drip obliges and goes to kill their infant son, too, but the Devil tells him not to; instead, Drip decides to leave some disturbing imagery for the police by leaving the baby among the scattered carnage of what's left of the wife. It's not until Drip sets him down that he realizes that the people he brutally murdered were his mother and father, the crying baby looking up at him is his infant self. Drip is horrified to realize that not only did he actually kill his parents, he's also the reason he was sent to live with the grandmother who's been sexually abusing him all his life (and, having died and ended up in the area of Hell that Drip rules, ''is still doing it''). The Devil points out that time works funny in Hell; Drip could have prevented it all if he had just chosen not to murder two strangers for a scarf.]]
233* ''Webcomic/{{SSDD}}'', Doctor Cook claims that he got on the Maytec board of directors using stock market information from a PDA that was accidentally sent back in time. But then he locked up the present day version of the PDA and made sure it was never sent back, he noted that the future version didn't disappear or anything.
234** Also the Anarchists were prevented from stealing the ''Wildfire'' time machine and using it to build the ''Inglourious'' fifty years earlier. Unfortunately they still have it, centuries before it wasn't built.
235* In ''Webcomic/WickedPowered'', much like the "All You Zombies" example, the main character becomes both of his own parents through time travel, gender-bending, and amnesia. His DNA therefore has no origin, and he is immortal because of this.
236[[/folder]]
237
238[[folder:Web Original]]
239* Tom Francis' [[http://www.pentadact.com/index.php/2007-02-28-machine-of-death-exploded "Exploded"]] (featured in the ''Literature/MachineOfDeath'' anthology) uses the "information" variant. Two guys invent a machine that predicts how one can die. While one can ''postpone'' one's predicted death, one cannot avert it entirely. The invention makes both men fantastically wealthy, and miserable. Late in the story, the machine's information is explicitly described as coming from the future.
240--> '''Narrator:''' But Pete kept saying something over and over to me that to this day I don't quite get: "It's a function of the future," he said, "not the past." He said it didn't matter what he did to it before it was built, because its predictions were somehow independent of anything that had already happened.
241* The Reversed Grandfather Paradox is lampshaded for all it's worth in ''WebAnimation/RedVsBlue'' when Church is send back in time and attempts to prevent the accident that started the entire time travel problem.
242** [[spoiler:Captain Flowers dying from a heart attack in his sleep?]] He died from the heart medicine Church gave him to prevent that.
243** The tank's AI named Sheila?
244--> '''Tank:''' ''"Welcome to the '[=M808V=] Main Battle Tank', you may call me 'Philis'."''\
245'''Church:''' ''Shiela, I-...Wait, Philis? Why not Sheila?"''\
246'''Tank:''' ''Name overwritten. You may now call me Sheila."''
247** [[spoiler:Sheila killing Church because of the friendly fire setting?]] Guess who changed the default setting.
248[[/folder]]
249
250!!Unclassed, multiple or [[TimeyWimeyBall confused]] Examples
251
252[[folder:Comic Books]]
253* The fear of this appears to be the reason why ComicBook/DoctorStrange, having traveled to the distant past and witnessing the Comicbook/FantasticFour having traveled to the same time and place for their own reason, is very reluctant to reveal himself to them. He has befriended them in the present, or rather ''his'' present, but the FF are from an earlier point in time and haven't met him yet.
254[[/folder]]
255
256[[folder:Fan Works]]
257* Improperly invoked in ''Fanfic/LightAndDarkTheAdventuresOfDarkYagami'', after Blud learns that Matt survived a car crash with "Yotsuba", he decides to write Matt's name in his Death Note in the future to kill him in the past. This results in the past changing, with Matt dying and Yotsuba surviving. Dark claims the reason why Blud is telling him and Light this now, rather than at the point in the future when he writes the name is "Its one of those time [[RougeAnglesOfSatin parradoks]] that they have in Franchise/BackToTheFuture".
258** Dark's exact words are "Oh I didn't tell you my death note can also kill people in the past and I am going to write his name in it in the future to kill him in the past and stop him stealing the death note." [[SarcasmMode Hope that clears up any confusion.]] It doesn't help that the flashback scenes go from "Present Day" to "Meanwhile in the Past" to "Back in the Future"
259* In ''Fanfic/MegamanStarForceOrion'', Amaya and Taisaka decide to go back in time to prevent Kiri from making contact with the Ice Goddess Talisman. With the help of the UMA Fire, they reach the year in which Kiri is exiled from her home. Fire then brings them 2 years forward in time, and Taisaka and Amaya meet Tagekai, who reveals that Taisaka was originally a member of Tri-Clan. This causes Taisaka to break down as Amaya abandons Taisaka, soon meeting Takeshi's former self. Takeshi later reveals he has memories of everything that occurred as he was 66, as he is trapped in that age. Taisaka changes herself by telling her younger self not to fight Tagekai which causes her to become exiled. Amaya and Taisaka bring Kiri to the Omnikron Temple, and Amaya meets Eidaya, explaining everything. This creates a major time paradox, which causes the already fragile sands of time to become even more fragile. Soon Amaya returns to the past, meeting his father, who realizes that Amaya is Amaya, and he travels after him. As Amaya tries to fix things in Tri-Clan, Takeshi reveals he killed Taisaka, and Daisuke King, a Time Traveling Kamen Rider, shows up and brings Amaya to the present. He warns Amaya that Ryo is about to be killed by a Shinigami named Albano, and if this were to happen, the future would be corrupt, as Takeshi would cease to exist in the present. At the same time, Amaya's father plans to force time into 11:60 PM on December 24th. Finally, Taisaka travels to the present from the past, creating a temporal corruption where memory demons overcome the present world and attempt to end the world. Time is eventually reset with the use of the Stolen Pocketwatch from the very first episode.
260* With [[Series/DoctorWho the Tenth Doctor]] traveling with [[Franchise/SherlockHolmes Holmes and Watson]] in ''Fanfic/ChildrenOfTime'', temporal paradoxes ''are'' a concern, as the Victorian duo ''do'' have fates to fulfill in their own time. The season finale revolves around this, specifically, what happens when something that should ''not'' have happened ''does''.
261* In the ''Fanfic/PonyPOVSeries'', there's actually a ''character'' who is more or less the embodiment of this trope. [[spoiler:Nightmare Eclipse is a [[FutureMeScaresMe potential future]] Twilight Sparkle in the BadFuture where Discord won. She caused a Grandfather Paradox by resetting the timeline so Discord never won in the first place. However, she decided to [[SuperpoweredEvilSide become a Nightmare]] and kill Discord in revenge for the hell she put him through, [[TheDarkSideWillMakeYouForget forgetting her reasons for resetting things to begin with]] and trapping him in a GroundhogDayLoop. However, she then proceeds to be the cause of an Ontological Paradox, manipulating events so Twilight will become her and reset the timeline, fusing with Eclipse and repeating the cycle next loop. Her doing this results in Apple Pie nicknaming her Nightmare Paradox.]]
262* ''Fanfic/TheLastGreatTimeWar'', a Doctor Who fanfiction, has a multiverse-wide war of paradoxes.
263* This short ''Franchise/SonicTheHedgehog'' comic has [[https://twitter.com/sonisis_/status/1152624480377688064 Silver the Hedgehog's time traveling creating 4 other Silvers]].
264[[/folder]]
265
266[[folder:Film]]
267* ''Film/AustinPowers: The Spy Who Shagged Me'' shows Austin briefly attempting to reason why no time paradox has occurred due to him and Dr. Evil time traveling to a date where they logically shouldn't be. Basil Exposition puts his mind at ease
268--> '''Basil:''' "I advise that you not worry about that sort of thing and.. just enjoy yourself [[AsideGlance (faces audience)]] that goes for you all too."
269--> '''Austin:''' (also facing audience) "Yes"
270* French-Canadian movie based from a cult tv show ''Dans une galaxie près de chez vous 2'' featured a spatio-dimensional rip (shaped like a zipper) who goes to present Earth. The Capitain was able to chuck down a DVD with their plea ([[GreenAesop NOT to destroy the ozone layer]]) recorded on it. It backfired when the video got featured on ''Website/YouTube'' and ridiculed as "[[http://en.wikipedia.org/wiki/Star_Wars_Kid Star Wars Twit]]" (Being bad at pronounciation dosen't help). Nevertheless, it might have pushed a younger version of the Capitain to go into space, directly ''and'' indirectly setting the events of the show into place.
271* ''Film/DejaVu2006'' contradicted itself on terms of this. First, it is implied that anything changed in past changes the present, as Doug causes the death of his partner, that was thought caused by the ferry explosion. Later, it is implied that the past has already been changed, as [[spoiler:the message "U CAN SAVE HER" in Claire's house was written by him]], but in the end, it is contradicted, because [[spoiler:if he prevented the explosion, he could never have been assigned to the case, and thus could never do the time travelling, and so on...]]
272* ''Film/Millennium1989'' concludes with a massive paradox barrelling its destructive way into the future whose time travel efforts caused it.
273* Played with in ''Film/{{Primer}}''. As one of the characters says, "The ''last'' revision is apparently the one that counts." We find characters gradually losing their worries about causality; they wind up going back in time to relive the events of that same week in their original place -- apparently intending to do everything ''right'' this time. It appears that causing a paradox causes some kind of mild brain trauma to the time traveler involved. But then there's that other version of yourself that you drugged up and locked in the basement so you could replace him...
274* The reason the universe is ending in ''Star Crossed'' is because of all the various paradoxes created by the Federation, from [[Series/StarTrekTheOriginalSeries Jim Kirk]] to [[Series/StarTrekVoyager Captain Janeway]].
275[[/folder]]
276
277[[folder:Tabletop Games]]
278* In the TimeTravel RPG ''TabletopGame/{{Continuum}}'', if a time traveler creates a paradox, they accumulate "frag," and if they accumulate too much, it eventually causes them to unravel. What's more, unchecked temporal paradoxes will eventually lead to the unraveling of reality itself. (On the other hand, the game totally mindscrews you with the fact it manages to be utterly fatalistic about it: the fact the universe itself exists, even if there is a paradox in existence, means that -- at some point -- the temporal paradox will be/does get/has been fixed, by the Continuum. It's just a matter of who or what becomes collateral damage in the process of fixing it.) Much of the game centers around the players, who are part of "The Continuum", trying to fix paradoxes deliberately created by time travelers (known as "narcissists") who don't believe the official line on paradoxes and who want to mess with the timeline for their own personal gain. Knowledge in itself never causes frag, though. There's nothing at all requiring you to learn information independently before giving it to your past self. Ontological paradoxes don't cause any frag unless an object is involved, in which case future you must replace the object without getting caught by present you before you give it to past you to fix the Frag from sending the object back.
279** More accurately, in Continuum, there are no paradoxes. The Continuum rulebook states outright HitlersTimeTravelExemptionAct works. If you tried to, for example, kill Hitler, even if you succeed, you will only "frag" yourself. Other time travelers, knowing full well reality must be paradox-free, will set up an amazing string of coincidences such that perceived history ''looks'' right. Thus, Hitler may have been assassinated any number of times, but because history has a Hitler in it, body doubles, cyborgs, actors, and whatever else was needed was done to keep ''reality'' intact. Joan of Arc, for example, is a time traveler, and she is fully aware her fate is to die in France in the Middle Ages; she has too many obligations ''now'' to go and do it, but figures she'll get around to it when she is bored of her current life. Or not; she might get a body double or clone or other means to apparently fulfill her destiny - what the game calls her Yet.
280** Similarly, the expansion sourcebook (currently trapped in DevelopmentHell) ''Narcissist'' has a different take on this -- the original time traveler entered the "main" timeline's past and introduced time travel sometime around 14000 BC. Said time travel directly resulted in a [[TheSingularity singularity]] around 2400 AD, which then used its super-powerful minds and infinite resources to make ''sure'' that said time traveler never leaves our timeline (which would require a portal made out of X number of Temporal Paradoxes), and that time travelers don't cause the timeline to deviate from the history that led to the singularity. In alternate timelines away from "the swarm" -- agents of the Singularity, named that because there's a lot of them, but they're disorganized idiots -- paradoxes ''don't exist'': "frag" exists in the main timeline specifically due to the singularity's agents constantly trying to time-MindRape anyone attempting to change history.
281* Time Travel is rare in ''TabletopGame/Warhammer40000'', but [[HyperspaceIsAScaryPlace the Warp]] does strange things sometimes, which may result in a ship setting out to answer what turns out to be its own distress signal. In another example, one kleptomaniac Ork Warboss was sent back through time via warp-storm, met up with his past self, and [[InsaneTrollLogic killed his temporal doppelganger so he could have two copies of his favorite gun]]. The resulting confusion stopped the Waaagh! in its tracks.
282* Averted in ''TabletopGame/GeniusTheTransgression''. As the game puts it, it turns out the universe doesn't particularly care if your grandmother gets shot and there's no shooter -- barring [[TimePolice external intervention,]] you pop out of existence if you pull the trigger and the bullet hits home. This can have some interesting consequences, as the angry young lad seeking to avert a massacre in his country's history [[RetGone did not ]][[IAmYourFather discover...]]
283* In ''[[http://dig1000holes.wordpress.com/time-temp/ Time and Temp]]'', a paradox would RetGone ''[[ApocalypseHow all of existence]]''. Office temps (hence the name of the game) are used as field agents to prevent this, because they're otherwise [[{{Mooks}} unimportant]] enough to minimize the risk of personal GrandfatherParadox - though their potential for [[NiceJobBreakingItHero incompetence]] is at odds with this.
284* The ''TabletopGame/{{GURPS}}'' Sourcebook ''GURPS TabletopGame/InfiniteWorlds'' includes a chapter exploring time travel and paradoxes.
285* A ''rules-based'' version of this appears in the ''Franchise/StarTrek Customizable Card Game''. At any time, a player may say the words "Devidian Door" and play a card from their hand for free. However, during their next turn, they ''must'' reveal and discard a card named "Devidian Door" from their hand. If they can't, then they've just caused a paradox, [[NonStandardGameOver and they lose the game right then and there]].
286[[/folder]]
287
288[[folder:Video Games]]
289* ''VideoGame/ShadowHearts1'' and its sequel, ''[[VideoGame/ShadowHeartsCovenant Covenant]]'' have a few, related to [[spoiler:good[=/=]canon ending of ''Covenant'']].
290** Yuri's TragicKeepsake, Anne's Cross, exists because of an ontological paradox. [[spoiler:He receives it from his dead mother, but gives it to one of his party members, Karin, in the second game. In the ending, Karin travels back in time, becoming amnesiac, and turns out to be Yuri's mother, who gives birth to Yuri and gives him the necklace upon her death, starting the loop all over again.]] The same can be said about [[spoiler:Yuri himself, as it's unlikely that Karin could be sent to the past if she didn't travel with Yuri in the first place]].
291** There's also [[spoiler:Yuri returning to the beginning of the first game [[PeggySue with his memories intact]]. It's implied that he can now save Alice from the Curse of Four Masks, leading to the good ending of ''[=SH1=]''. However, if Alice survives, then events of ''Covenant'' won't happen as they did, and thus Yuri won't be sent to the past to save her. Although it's possible that these events happen in BroadStrokes, likely breaking the time loop]].
292[[/folder]]
293
294[[folder:Visual Novels]]
295* ''VisualNovel/{{SOON}}'': Averted. Time travelling to a certain date resets any changes caused by Atlas from that point and on. To progress, the player has to be careful not to undo their own work this way.
296-->'''Teen!Atlas:''' But before you go... can you tell me about the future? Or would that cause a {{time paradox}}?\
297'''Atlas:''' ''[thinking]'' Ah, kids and their time paradoxes. So adorable. ''[aloud]'' Come on Atlas, you know in your heart that the branching multiverses model is the only one that makes sense.\
298'''Teen!Atlas:''' Haha, yeah, sorry older me.
299* ''VisualNovel/TimeHollow'' avoids these, for the most part, by having a few people [[RippleEffectProofMemory remember all alterations]] - as such, you can't hit the "prevent myself from adjusting time" snag by fixing the thing you wanted to change. There is, however, of all things, a [[spoiler:cat]] that ends up in a near-ontological paradox avoided only by the fact that [[spoiler:it's locked in time and cannot age.]]
300[[/folder]]
301
302[[folder:Webcomics]]
303* In the first story arc in ''Webcomic/BlackHole2019'', main character Diana Nox deals with a caveman who was mysteriously sent to the present. After sending him back to his proper time with her SexMagic, Diana inadvertently changes history due to teaching the caveman modern concepts of sexual relations and apparel (i.e. kissing, the missionary position and wearing lingerie) and him introducing those concepts to his mate.
304* ''Webcomic/BreakpointCity'' has several examples. Some are played straight, some are... not. A few have been explained away as due to alternate universes, therefore probably not a paradox, but you never know.
305* [[https://web.archive.org/web/20150905141225/http://www.cheercomic.com/?date=2008-01-31 This is confusing.]] How is a flashback to the childhoods of the ''Webcomic/{{Cheer}}'' girls even possible? Weren't they, you know, ''boys''? Just how much of the past did Miranda rewrite to cover up Anne's mistakes? Is it like what happens when a Webcomic/{{misfile}} occurs? Argh...maybe it's best to pretend this isn't canon, especially seeing as there are [[http://thewotch.com/index.php?epDate=2005-10-11 lots of]] [[http://thewotch.com/index.php?epDate=2005-10-19 people]] [[https://web.archive.org/web/20150905135448/http://www.cheercomic.com/?date=2006-05-30 who still remember.]]
306** Well, three of the girls do not remember ever being anything ''but'' girls, so presumably their memories were altered. [[PlotHole As for Jo...]]
307* In ''Webcomic/DragonMango'' [[http://dragon-mango.com/comic/chapter03/dm03-28.htm you have to ride the rollercoaster-- because you're already getting off.]]
308* In the Surreptitious Machinations arc of ''Webcomic/GeneralProtectionFault'', Empress Trudy travels back in time to give her younger self the necessary information on what she must do to take over the world. Near the end of the arc, Nick and Ki's son Todd reveals that the entire BadFuture he and Empress Trudy came from was the product of a temporal paradox, since it could not have happened without Empress Trudy advising her younger self, which would not be possible if it did not previously exist. It is heavily implied that [[spoiler:Pandemonium]] was responsible for the existence of the alternate future in the first place. As a result of the future being changed, Todd, the Empress and all other objects from the alternate future fade from existence, but the Empress teleports to a different time just before she fades, and the Gamester finds and recruits Todd.
309* [[http://rockpapercynic.com/index.php?date=2008-11-14 This]] ''Rock, Paper, Cynic'' comic. A man uses an axe to murder someone and get at a time machine. He then briefly experiments with it before realizing that he doesn't know where his alternate self that should exist is. Then, by intention or accident, he goes back to the moment first chronicled in the comic, where he becomes the man his past self killed to get at the time machine.
310* In ''Webcomic/SailorMoonCosmosArc'', because of the Chibiusa of the 21st century traveling through time and being present in the final battle, she was reincarnated along with the other senshi. ''However'', because the other senshi were revived in the ''30th'' century, the Chibiusa that was born to Usagi and Mamoru never ended up traveling in time, therefore, unlike the other senshi, has no memories of her past life and has never awakened as a senshi. [[spoiler:It's because of an unconscious wish Usagi had that Chibiusa would never awaken as a senshi.]] There is one more twist to this: [[spoiler:the memories of the time-traveling Chibiusa were sealed inside the Pink Moon Crystal, so when she broke her brainwashing and started receiving her powers, she finally gained the memories of her past self]].
311* ''Webcomic/{{Subnormality}}'' has [[http://www.viruscomix.com/page564.html The Mission]], which holds a Reverse Grandfather Paradox - [[spoiler: the traveler spread the teachings of the holy book he adored, but it turns out HE was the propogator of that holy book.]] [[LogicBomb So where did those teachings originate?]]
312* ''[[Webcomic/SomethingPositive Super Stupor's]]'' Clockstopper can change history with his "Time Punch". (And he'd [[http://www.superstupor.com/sust02132009.shtml rather be surfing]] [[ShoutOut TVTropes]] than fighting crime.)
313[[/folder]]
314
315[[folder:Web Animation]]
316* ''WebAnimation/DeathBattle'': "Goku Black Vs. Reverse Flash" gets pretty confusing after a while, because both are living temporal paradoxes who can travel in time and can't be killed permanently.
317[[/folder]]
318
319[[folder:Web Original]]
320* The end of ''Website/TheOnion'' article "Pistorius Case Takes Dramatic Turn As Altered Plane Of Reality Results In Paralympian Shooting John Lennon": ''At press time in November of 1986, South African officials reported they have apprehended a newborn Oscar Pistorius for the murder of John Lennon, thereby preventing the deaths of both Reeva Steenkamp and John Lennon at the hands of a 26-year-old Oscar Pistorius, and thereby making Pistorius a free man.''
321[[/folder]]
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