History CharacterDerailment / WesternAnimation

!!Individual examples:* ''WesternAnimation/KingOfTheHill'':

!!Individual examples:
* ''WesternAnimation/FamilyGuy':
** Quagmire definitely derailed in a ridiculous vendetta against Brian, despite the similarity of both characters; listing ridiculous reasons-- including, of all things, Brian's secret desire for Lois, despite Quagmire being guilty of the same thing; while Brian's desire is out of genuine love and romantic interest for Lois, against Peter's man-child ways, and Quagmire is simply a shameless pervert wanting what he can't have, including preying on Lois in a public restroom.
Quagmire's inexplicable hatred for Brian, rather, seems to be a "Dennis Miller" like post-9/11 hypocrisy, of Quagmire being an airline pilot, and Brian being an arch-liberal; meanwhile Seth MacFarlane voices both characters, and he narrowly avoided being a victim of 9/11 when he drunkenly missed his flight, which turned out to be one the planes that struck the Twin Towers. Likewise MacFarlane denied the event having any effect on him, while was basically a real-life version of Brian's liberal self; however this conflict seems the most likely explanation for the derailment.
* ''WesternAnimation/KingOfTheHill'':

* ''WesternAnimation/MiraculousLadybug'' does this with one of its more prominent characters, Chloé Bourgeois. While Chloé starts out antagonistic, throughout Seasons 2 and 3, she goes down a slow, but firm HeelFaceTurn throughout those seasons, only for that development to be sidelined in the Season 3 finale, resetting her back to the AlphaBitch status she previously had. Following this in Season 4, any glimpse of hope she had was flattened, where she goes from being willing to commit a SelfSacrificeScheme during the episodes "Zombizou" and more recently "Ladybug" (where she shields her ExtremeDoormat friend Sabrina from a Scarlet Akuma). But, not even half a season later, and she has that same friend locked in a closet doing her homework.

* ''WesternAnimation/MiraculousLadybug'' does this with one of its more prominent characters, Chloe Bourgeois. While Chloe starts out antagonistic, throughout Seasons 2 and 3, she goes down a slow, but firm HeelFaceTurn throughout those seasons, only for that development to be sidelined in the Season 3 finale, resetting her back to the AlphaBitch status she previously had. Following this in Season 4, any glimpse of hope she had was flattened, where she goes from being willing to commit a SelfSacrificeScheme during the episodes "Zombizou" and more recently "Ladybug" (where she shields her ExtremeDoormat friend Sabrina from a Scarlet Akuma). But, not even half a season later, and she has that same friend locked in a closet doing her homework.

** Randy Marsh's gradual transition from [[StandardFiftiesFather calm and responsible father]] to creepy immature ManChild is seen as an example of this by many. Definitely a case of DependingOnTheWriter, though, as some episodes still portray him as a pretty normal and responsible father.

** Skarloey and Rheneas, previously two of the oldest and wisest engines on the island, are now childish and afraid of ''everything'' (from thunderstorms to the incline yards to ''the wharf''), while Sir Handel of all engines is turned from the [[{{Jerkass}} jerkiest]] of the narrow-gauge engines to the kind voice of reason.
** Thomas himself was once depicted as friendly and helpful, [[SmallNameBigEgo if somewhat cocky and brash]]. He's now excessively pushed to make appearances in every single episode (even episodes about the narrow gauge engines) and dispense advice to everyone; when he isn’t the subject of the episode where [[AesopAmnesia he keeps being taught the lessons he's already learned]] or even developing [[CompressedVice Compressed Vices]] that is.

** Omnitraxus was originally depicted as a mentoring guide and a ReasonableAuthorityFigure who guided Star into growing up to be a stronger woman. However, he, like the other members of the commission, suddenly became shady and racist bigots and went as far as helping Mina Loveberry ravage Mewni without question

* ''WesternAnimation/MyLittlePonyFriendshipIsMagic'': King Sombra [[GenericDoomsdayVillain didn't have much character]], but what was shown in flashbacks and present to be a ColdHam, NoNonsenseNemesis smart enough to [[NearVillainVictory nearly win]] despite never directly confronting the heroes [[CrazyPrepared due to all the precautions he took to safeguard his weakness over 1000 years prior]]. Upon [[BackFromTheDead his resurrection]] by Grogar in the final season premier, he's inexplicably a LargeHam and SmugSnake who, after his smart plan to [[spoiler:fake defeat by the Elements of Harmony to follow them to their source and destroy them]], succumbs to [[VillainBall regular villain pitfalls]] of [[BondVillainStupidity leaving the heroes be after imprisoning them]] and failing to flea when things turn against him, with Grogar expecting him to be so inept he'd serve as an example to the other villains. Much FanWank ensued arguing this was do being [[CameBackWrong resurrected improperly]] or actually being a clone/replica, perhaps deliberately changed to serve Grogar's plan. [[spoiler:This turned out more plausible once it was revealed that "Grogar" was a disguised Discord who did it to teach the heroes confidence, but it's never stated if he changed anything intentionally or not.]] Note that Sombra's old ([[FlatCharacter lack of]]) characterization was [[BaseBreakingCharacter controversial enough]] the change wouldn't have been seen as so objectionable if not for it [[CanonDiscontinuity decanonizing]] his comic book portrayal which fleshed him out into a complex, TragicVillain while keeping his original traits which even many who didn't care for the comic saw as a superior portrayal.

** Skarloey and Rheneas, previously two of the oldest and wisest engines on the island, are now childish and afraid of ''everything'' (from thunderstorms to the incline yards to ''the wharf''), while Sir Handel of all engines is turned from the [[{{Jerkass}} jerkiest]] of the narrow-gauge engines to the voice of reason.

** Percy went from a mischievous CloudCuckooLander to a naive, forgetful moron who can't pronounce simple words, Toby was a kind and confident CoolOldGuy but later became a wimp with self-esteem issues, and Skarloey and Rheneas, previously two of the oldest and wisest engines on the island, are now childish and afraid of ''everything'' (from thunderstorms to the incline yards to ''the wharf''), Thomas himself was once depicted as friendly and helpful, [[SmallNameBigEgo if somewhat cocky and brash]]. He's now excessively pushed to make appearances in every single episode (even episodes about the narrow gauge engines) and dispense advice to everyone; when he isn’t the subject of the episode where [[AesopAmnesia he keeps being taught the lessons he's already learned]] or even developing [[CompressedVice Compressed Vices]] that is.

** Percy went from a mischievous CloudCuckooLander to a naive, forgetful moron who can't pronounce simple words, Toby was a kind and confident CoolOldGuy but later became a wimp with self-esteem issues, and Skarloey and Rheneas, previously two of the oldest and wisest engines on the island, are now childish and afraid of ''everything'' (from thunderstorms to the incline yards to ''the wharf''). Thomas himself was once depicted as friendly and helpful, [[SmallNameBigEgo if somewhat cocky and brash]]. He's now a poorly-written CreatorsPet that is obligated to make appearances in every single episode (even episodes about the narrow gauge engines) and dispense advice to everyone.

* ''CharacterDerailment/CloneHigh''