History TemporalParadox / WesternAnimation

** Fry's genetic material. Being [[spoiler:[[MyOwnGrandpa his own paternal grandfather]]]], the question is where exactly the information carried on his y-chromosome originated.

* Naturally enough, ''WesternAnimation/BillAndTedsExcellentAdventures'' often courted this trope. One obvious example is the episode in which Bill and Ted neglect to buy Bill's father an antique railroad watch as a birthday present, to replace the one he lost as a child. Ted's initial plan is actually perfectly sound: [[StableTimeLoop take the original watch from Bill's father when he 'loses' it in the past, then give it to him in the present.]] This plan fails however, so they travel even further back in time to obtain the watch ''before'' Bill's father inherits it. Of course, this should mean that Bill's father wouldn't miss the watch in the first place, but the episode [[BellisariosMaxim simply ignores this]].
* The ''WesternAnimation/DannyPhantom'' [[MadeForTVMovie movie]] ''WesternAnimation/TheUltimateEnemy'' is one big temporal paradox. In the original timeline, Danny'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."
* Thankfully averted in ''WesternAnimation/DuckTales2017''. One episode has Dewey being dropped into the past with a younger Donald and Della Duck. At the end of their adventure, Dewey ''tries'' to warn Delila about her terrible fate, but both ducks stop him.

(''Donald and Della's [[OhCrap eyes go wide]], quickly clamp his beak shut'')\\

'''Della:''' No! Can't warn us about the future! You'll disrupt the timestream!\\
'''Donald:''' Have you watched any movies?!
* In ''WesternAnimation/InvaderZim'', an entire episode (Bad Bad Rubber Piggy) has one scene that demonstrates this perfectly: After GIR finds out that Zim intends to send a robot back to the past to destroy Dib, it leads to this classic line of dialogue:
-->'''GIR:''' Wait... if you destroy Dib in the past, then he won't ever be your enemy, so you won't have to send a robot back, so then he will be your enemy, so then you WILL have to send a robot BACK... ''(head explodes)''
* Starlight Glimmer's revenge plot in ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' results in this: she travels back in time to prevent the Sonic Rainboom that gave the Mane Six their Cutie Marks...to get revenge on them for foiling her actions in Our Town in the season premier, meaning she'd negate her own reason for going back in time in the first place. Though her and Twilight seem to be immune to the timeline changes. Unlike many events, this actually ''does'' cause serious issues: each change to the past she makes causes a BadFuture worse and worse than the last [[note]]Although the simple fact that Twilight Sparkle is able to visit several altered futures is left unexplained : Nightmare Moon's return was the first catastrophy which the main characters stopped, but no trace of it subsists in several alternate futures, ruled by villains who showed up ''after'' the Mare in the Moon. But WMG is probably here to solve this.[[/note]]

* ''WesternAnimation/SuperFriends''. In the ''Challenge'' episode, "Secret Origins Of The Super Friends," the Legion of Doom tries to change history by messing with the origins of Superman, Wonder Woman, and Green Lantern. Okay, but seeing as how much of Super Friends is based on Pre-''ComicBook/CrisisOnInfiniteEarths'' lore and hence Luthor's baldness and StartOfDarkness were both accidentally caused by Superman when he was Superboy, how can Luthor-- and as its founder, the Legion of Doom itself--exist if Superboy was never there to cause what happened to Luthor? Likewise, given his origins even Pre-Crisis involved someone copying Superman, how does Bizarro continue to exist as well? This also applies, to a lesser extent, to the others. Sinestro's crimes were exposed by Hal Jordan; maybe eventually, someone else would have, but it was Hal's newbie attitude that caused him to question an otherwise model Green Lantern; shift the timeframe and he maybe never meets the [=LoD=]. Most Cheetah origins have Wonder Woman involved in some way, at least some as Cheetah feeling challenged by her existence. Also, take Luthor grabbing Abin Sur's ring. That might get the Guardians' attention. Also, without those three, and especially Big S, would the SF have even formed, and since the [=LoD=] formed out of fear of this group…the list goes crazy on. Ah, everyone know time travelers are [[AWizardDidIt surrounded by a temporal bubble]] that prevents them from being affected by their own alterations in the timesteam. The real question is: if the Legion of Doom could see through time to spy on the "secret origins" of the heroes, how do they not know the entire Justice League's secret identities?

* This possibly happening is why Della and Donald refuse to let Dewey (Della's son and Donald's nephew) warn them about the future in the ''WesternAnimation/Ducktales2017'' episode "Last Christmas".
-->'''Donald:''' NO! KEEP YOUR MOUTH SHUT!\\
'''Della:''' You ''can't'' warn us about our future, you'll disrupt the time stream!\\
'''Donald:''' Haven't you ever seen ''any'' movie?!
* In the first ''WesternAnimation/{{Futurama}}'' [[TheMovie movie]], the "paradox-free time travel" isn't quite paradox-free: [[spoiler:there remains an ontological paradox surrounding the origin of the name "Lars," as future-Fry chose that name when he realized that the injuries he sustained when Bender attempted to kill him made him Lars.]] From whence did the name come?
** Well, if we just accept that [[spoiler: there is no 'beginning' to the Lars and Fry cycle, then it all works out nicely. Fry says "Ow, my larynx", but it comes out as "Lars", at which point he realises "Oh hey, I look and sound like Lars now, I guess I ''am'' Lars!"]]
** Additionally, the temporal tattoo is an ontological paradox. At the end of the movie, Bender peels it off Lars's ass, takes it back in time, and puts it on the present Fry's ass. Thus, it was never actually created, and just loops through time eternally with no beginning or end.
** Fry's genetic material. Being his own [[spoiler: paternal grandfather]], the question is where exactly the information carried on his y-chromosome originated.
** One episode had Leela being the campaign manager of a Senator who had [[SetRightWhatOnceWentWrong traveled back in time to become the president of the world in order to prevent an apocalypse.]] He wins the election, but unfortunately invokes a paradox, which is explained by Bender. Since he changed the past, that would mean that he wouldn't have traveled back in time in the first place. The Senator disappears via ResetButton, and Nixon is reelected.
*** Not only that, he went back in time using the same method as in the aforementioned movie. So much for "paradox-free" time travel.
*** This brings along FridgeHorror, since this means that in about 20 years, there will be an apocalypse led by robots.
*** This same paradox occurs in "The Why of Fry" with the Scootie Puff, Sr. but there it works out just fine (Fry tells Nibbler in the past to give him a better escape craft during the Infosphere mission, the Nibblonians give him one, and he escapes before the quantum interface bomb sends the Infosphere to the other dimension, which is not what happened the first time and invalidates the event that made it possible for him to go back in time in the first place).
** Most if not all of the above is due to said "Paradox-Free" time travel actually being "Paradox-''correcting''" time travel: paradoxes come into existence repeatedly, but radiate enough doom that the universe actively kills them before they can do any damage. The only time this backfired on the universe was when the army of Benders was "corrected" all at the same time.
* ''WesternAnimation/{{Gargoyles}}'': Time travel always creates a StableTimeLoop:

* In the ''WesternAnimation/KimPossible'' three-parter "A Sitch in Time", future-Shego gives present-Shego a plan to use the Time Monkey to {{take over the world}}. Coming up with this sort of plan [[BrilliantButLazy on her own initiative]] isn't really like her -- but she didn't have to, she just had to remember what she'd been told and go back in time to repeat it to herself.
* In the ''WesternAnimation/MiloMurphysLaw'' episode, "Missing Milo", Milo, Cavendish and Dakota get stopped from running into a group of mutant pistachio monsters when a peach gets thrown at Cavendish which is then pocketed by Dakota; later after time traveling to 15 minutes in the past and seeing their past selves about to run into the mutants, Dakota hands the peach to Cavendish who uses it to stop themselves. This then leads to the two of them having a looping conversation about where the peach came from.

''(repeats)''
* This happens in the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' episode "It's About Time". Twilight Sparkle meets her future self, who tells her that she was able to get here because of the time spells located in the Star Swirl the Bearded wing of the Canterlot Archives. Later in the episode, she goes there (for entirely different reasons) and ends up using a time spell...to go back and tell herself about the time spells. Hmm, now where did she learn about the location in the first place?
** The whole episode is this. Past Twilight is so bewildered and amazed by the concept of time travel that she can't shut up, and future Twilight doesn't manage to tell her what the actual thing she's supposed to be averting is before she gets sucked back to the future: all past Twilight knows is that future Twilight was from the following Tuesday. So she spends the week panicking about it, ends up with all the injuries future Twilight had when she visited, and by Monday night concludes the only way to stop whatever will happen by Tuesday from happening is to stop time. [[spoiler:So she goes to the archives, but as Tuesday morning arrives, nothing happens, but she finds the time spell and goes back in time to warn herself not to worry about the future...]]
* The ''WesternAnimation/StarTrekTheAnimatedSeries'' "Yesteryear" revolves around a Reverse Grandfather Paradox in which Spock prevents his own death as a child. He doesn't do it quite right this time around, resulting in a slightly revised timeline when he gets home. Originally, [[spoiler: his pet had lived. This time, he arrives a moment late, and the pet dies.]]
* In ''WesternAnimation/TheTransformers'' episode "[[Recap/TransformersG1WarDawn War Dawn]]", the Aerialbots are sent back in time trying to destroy the Decepticons' time machine. This puts them back at the start of the war, right at the start of one of the very first Decepticon attacks. While they try to stay out of the way, the end up saving a insignificant, not important dock worker. As it turns out that insignificant dock worker was the un-upgraded Optimus Prime, both giving the Autobots a leader and keeping the Decepticons from winning an important first battle, getting an advantage over the Autobots and likely winning the war. It was Optimus who had the Aerialbots created in the first place.

* ''WesternAnimation/TheFairlyOddParents'' special, "The Secret Origin of Denzel Crocker". Timmy goes back in time to find out why Crocker was so miserable and to try to fix it. He finds out that as a child, Crocker ''himself'' had fairy godparents--and that they were Cosmo and Wanda, something that they don't remember--and figures out that he must've done something to lose his fairies. He tries to warn the young Crocker, but inadvertently ends up being the one who reveals the secret (with some help from both '70s Cosmo ''and'' modern Cosmo's stupidity). Furthermore, as Jorgen shows up to erase everyone's memories of there being fairies, young Crocker manages to get his hands on the DNA tracker that AJ had built so that they'd know when Crocker was around, ''and'' managed to get Cosmo's DNA to use in it, ''and'' managed to covertly write a memo on the back of it that fairy godparents exist without Jorgen noticing, allowing him to keep that knowledge after his memory of fairies was erased...which means that if Timmy had never interfered, Crocker would be neither miserable nor fairy-obsessed. However, whereas when Timmy left for the past, Crocker was using a very primitive and likely useless "fairy finder", the Crocker in the present that Timmy returned to was using the tracker that AJ had built, implying that he ''had'' created an alternate timeline, and leaving one to wonder what happened in the original timeline. Of course, considering it's explicitly stated in TheMovie that few kids keep their fairies past their first year, much less until adulthood when they would leave ''anyway'', we can guess...
** Well the original timeline seems to be that 70's Cosmo is that cause of Crocker losing him and Wanda. Timmy then stops this incident only for present day Cosmo to turn on the mic while Timmy is talking and cause the incident to happen anyway. While this doesn't explain how Crocker knew about the existence of fairies after his mind was wiped in the original timeline, since we don't see the original incident play out, we can just assume any number of reasons for that. (Perhaps he managed to write a note in that timeline too.)
** There was also a HistoricalInJoke to imply that it was an alternate timeline.

** Lord Chronos was at first a meek scientist who invented time travel. He used it to steal things from history that would not affect the timeline. Then his wife nagged him about his lack of imagination, and one trip to the Wild West later he decided that stealing the most famous items from history and setting himself up as master of space and time was the better way to go. Reality itself falls apart, so he decides to go to the beginning of time and do it all over again. Batman and Green Lantern manage to reset history. Batman also manages to create a close AndIMustScream moment by trapping him in an eternal loop of his wife's naggery.
** Time travel itself seems perfectly fine: Superman went to the future and the past, the Justice League went to WWII, [[ComicBook/BoosterGold one of the team is from the future]], and the list goes on. Vandal Savage notes that his time machine couldn't send him back to a period where he already existed, [[FridgeBrilliance which may be with good reason]]: in that episode, time was falling apart only when Batman was with his very old self.

** Time travel itself seems perfectly fine: Superman went to the future and the past, the Justice League went to [=WWII=], [[ComicBook/BoosterGold one of the team is from the future]], and the list goes on. ComicBook/VandalSavage notes that his time machine couldn't send him back to a period where he already existed, [[FridgeBrilliance which may be with good reason]]: in that episode, time was falling apart only when Batman was with his very old self.