History CharacterDerailment / WesternAnimation

** While [[RescuedFromTheScrappyHeap it may have redeemed her in some eyes]], the Mistress' overall portrayal in "Stingstress" was ridiculed. Suddenly, the Mistress [[TookALevelInDumbass was revealed to be]] ''[[TookALevelInDumbass incredibly]]'' [[TookALevelInDumbass easily fooled by the presence of a man she found attractive]], was portrayed as lovesick for him, and weepy and emotional at being pushed around. Then her change at the end as "Hippie Mistress", revealing that she only needed one good experience of sex to loosen her up (and realize that she didn't need any men or the Superjail), was further seen as this for some (especially for [[ShipSinking the dejected shippers of Warden/Mistress]]).

** On the other hand, some consider [[spoiler: Cotton]] to have undergone a case of derailment during [[spoiler: his final appearance]], which {{retcon}}s his grudge against the Japanese despite him having [[spoiler: forgiven them in an earlier episode, talked out of his scheme to spit in the Emperor's face by his illegitimate son Junichiro]]. This gained the episode criticism from some viewers since while Cotton was not well liked, the way he [[spoiler: forgave the Japanese]] was considered development.
** Peggy originally started out as a well-meaning wife and mother, as well as being pretty sociable and having a fair amount of friends to hang out with and being rather fluent in Spanish. As the series went on though, she slowly became more and more narcissistic, and while still caring for Hank and Bobby, was not afraid to call them out if they did something that even slightly annoyed her, while her group of friends was slowly narrowed down to Nancy and Minh, and her Spanish became so terrible that it was used as a plot point once to get her out of a court trial.
** Hank had also undergone Derailment as the show went on. During the first few seasons, he was shown to enjoy Rock and Roll and practiced guitar at times and open to new things, despite his usual staid and conservative attitude. By the end he was a stuck-up tightass who was so old-fashioned you'd think he was Amish and views things out of his comfort zone with contempt and disdain.
** This is addressed in the episode "Get Your Freak Off", where Hank discovers Bobby has been listening to foulmouthed gangsta rap. He initially encourages Bobby's interest in a boy band he considers clean cut and safe- until he, Bobby, and Bobby's girlfriend go to a concert and begin dancing provocatively. Bobby's girlfriend has ridiculously permissive parents, which leads to a situation Bobby and even his girlfriend weren't comfortable with, and Hank comes to the rescue and teaches the kids to play an age appropriate game. While initially seeming to uphold Hank's uptight views as the best way to raise a child, it does show how extreme (and boring) Hank had become, and the ending shows him lightening up quite a bit.

* Many of the characters in ''WesternAnimation/ThomasAndFriends'' have suffered from character derailment, to varying degrees:
** Edward, previously an old, kind and wise engine, became younger and ruder in later seasons.

** Some derailments have been taken a different way in the CGI series, either reversed back, exaggerated or taken a different way altogether. Skarloey is back to his more mature and no nonsense persona, while Edward is kind again, albeit [[ExtremeDoormat to a fault]], unable to say no to others and easily dissuaded from his work. Thomas interchanges between his older and newer persona to erratic extremes while Toby's meekness has reached [[WesternAnimation/MyLittlePonyFriendshipIsMagic Fluttershy]]/[[WesternAnimation/{{Rugrats}} Chuckie Finster]]/[[Franchise/SuperMarioBros Luigi]] levels, being afraid of nearly anything that moves.
** Thankfully though, starting with Season 17, which came with a brand new writing team determined to return the show to its roots, [[CharacterRerailment almost everyone of the characters above have returned to their original selves]].

* Pam in ''WesternAnimation/{{Archer}}'' became a completely different character as the series went on. Starting off as a pleasant but lonely and depressed HR rep, she turned into a sex-crazed, drug addicted complete loon. Though as always, Administrivia/TropesAreTools, as many fans enjoy this version of Pam ''much'' more.

** Stan Smith went from a liberal and mature if somewhat overreactive man to a [[PsychopathicManchild complete psychopath]] in later episodes, although he ocasionally showed signs of his later characterization in the golden seasons. However, he still retains a moral attitude, even in later seasons, but still acts foolhardy.

** Roger also belongs on the list as in the start of the series, he is seen as a sensitive if somewhat snarky pushover but transforms to a total sociopath willing to kill, manipulate, emotionally scar, and ignore others for his own personal ambitions. Stan, despite being on the list himself and does things no different or worse compared to Roger, is disturbed by his antics. He also went from being a clandestine shut-in, with entire episodes revolving around the Smith family's attempts to conceal an alien from the public and the government, to quickly becoming so adept at dressing up in his costumes that his visibility in public is no longer implied to be dangerous.

* ''WesternAnimation/Ben10'''s DarkerAndEdgier sequel, ''WesternAnimation/Ben10AlienForce'', has Ben and Gwen exhibit different personalities than before, but that's excusable since it's been five years and they've matured. However, there is NO explanation for the change in Kevin, who not only has suffered massive BadassDecay, but is now a [[HeelFaceTurn good guy]] for poorly constructed reasons and shows [[SameCharacterButDifferent no signs of the sociopathic cruelty he did in the original series.]] Now all he can do is be blunt, demonstrate TheWorfEffect, drive them around in his beloved car, and occasionally thrive off of his reputation from back when he was an actual threat. Both ''Ultimate Alien'' AND ''Omniverse'' made attempts at CharacterRerailment, but the fanbase remains perpetually divided over how well either of them went.
** [[BigBad Vilgax]] went through some change as well; ''Alien Force'' portrayed him as LawfulEvil (though it lasts only one episode and it's strongly hinted he was actually ''posing'' as such for his own advantage; in later episode, he has ''no problem'' breaking laws); later, ''Ultimate Alien'' portrayed him as a ManipulativeBastard, which, while being some derailment in a way, was actually good and ended up being an AuthorsSavingThrow after the BadassDecay he had suffered in Alien Force.

** The entire franchise has a very complex case with titular protagonist Ben Tennyson; he started out as a immature brat, an IdiotHero and a CrouchingMoronHiddenBadass with a major ChronicHeroSyndrome, before being evolved into a more mature and competent character in ''WesternAnimation/Ben10AlienForce''. Come season 3 of Alien Force, he TookALevelInJerkass [[TookALevelInDumbass and in Dumbass]] due partially to an AcquiredSituationalNarcissism and partially an attempt from writers to make him more like his original self. WesternAnimation/Ben10UltimateAlien tried to balance his maturity and immaturity, with more or less successful results depending on the episodes and story arcs. Finally, come ''WesternAnimation/Ben10Omniverse'', the character has seemingly lost most of his maturity and competence he gained through the Alien Force[=/=]Ultimate Alien era, and ended up all the way back to his characterization from the original series.
* 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 her [[JerkAss Mean Girl]] 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.

** [=SpongeBob=] himself started out as a naive, yet kindhearted guy who cared about everyone no matter what, and had the innocence of a child. He later gets derailed into to an obnoxious, ManChild who pesters everyone he knows to play with him. He is often careless of others' safety, and cries and screams when his "friends" aren't around. He can even be a {{Jerkass}} once in a while, most notably in "A Pal For Gary".
** [[TheDitz Patrick]] got progressively dumber as the series went on. He goes from average intelligence in the first season to TheDitz in season 2 and 3 to virtually brain-dead in season 4 and onwards. He also became more of a {{Jerkass}} on occasion.

** Plankton however started out as a competent, aggressive and maniacal villain. Once TheMovie rolled around he lost much of the latter in favor of being either too obnoxiously happy with the few moments he seems to succeed, or constantly moaning and crying about what a failure he is. He's also lost a lot of competence, to the point that his DeadpanSnarker computer wife Karen often has to tell him how to do every basic step (even blink) with Plankton often [[GladIThoughtOfIt taking credit for her suggestions.]]
** Karen herself was always a BeleagueredAssistant, but was initially genuinely loyal and caring to Plankton despite her snarky qualities. Following the [[UnCanceled UnCancellation]], she has seemingly [[TheEeyore lost all sense of enthusiasm]] and openly vents her utter contempt for Plankton, placing him into high order HenpeckedHusband territory. In seasons 11-12, her main role is to make jokes about how stupid Plankton's plans are (such as going off to watch a movie or even unplugging herself so she doesn't have to hear it).

*** Though, really, this change was happening even in some of the ''Looney Tunes'' shorts of the late-1950s and early-1960s. Witness Bugs's cartoons with Daffy Duck during that time period: he usually played the more sensible StraightMan to Daffy's hyper-idealistic [[StealthPun loonatic]] persona.

** In the WesternAnimation/WileECoyoteAndTheRoadRunner shorts in the [=DePatie=]-Freleng era (most notoriously by Rudy Larriva) the Road Runner actively fights back against Wile E. Coyote, something he rarely, if ever did in the original Chuck Jones shorts[[note]]Jones made 9 rules for the Road Runner shorts, one of which being that the Road Runner cannot harm the coyote except by going "beep-beep"[[/note]]. This continues into 2003's "WesternAnimation/TheWhizzardOfOw" and the CG shorts from ''the Looney Tunes Show'',which kept the {{Slapstick}} nature of the franchise, unlike the show proper, such as "Silent but Deadly".

* Bloo in the Pilot of ''WesternAnimation/FostersHomeForImaginaryFriends'' and Bloo during the main show are practically two different characters. Bloo in the pilot and some of the earlier episodes is a friendly and well-meaning but mischievous imaginary friend who likes to have fun. In the rest of the series he's just a {{Jerkass}} who will do anything to get what he wants and loves being stupid and breaking the rules.

** Cosmo is the show's main offender of this. It was established in the first season that he ''ran away'' from home to marry Wanda. In another episode he broke down crying from having to be away from her overnight. It was very clear they enjoyed their relationship. Then, suddenly, in seasons four and five he was drooling over every attractive woman that came onscreen, repeatedly calling Wanda a nag and more, and acting like she had BoundAndGagged him at the altar. Hell, the original ''Oh Yeah! Cartoons'' shorts of ''Fairly [=OddParents=]'' had him be a lot different. Compare the calm, deeper-voiced Cosmo who was Wanda's equal intelligence-wise and actually seemed to share a loving relationship with his wife. Now, compare that to the sociopathic ManChild with the screechy voice portrayed in the Fairly Odd Parents series and see how far he fell. It's rather handy, you can tell his intellect by his voice pitch. Deep/slightly high voice, reasonable degree of smarts, really high voice, no smarts.
** Vicky went from just using tapes, recordings, personal belonging-destruction and other tiny bits of humiliation to torture Timmy to being armed to the teeth with chainsaws, maces, and other over-the-top weaponry and cackling maniacally all the while. This derails Vicky from as far back as the ''first'' episode, where she clearly shows she'd ''never'' want Timmy to suffer any serious physical harm, let alone be the cause of it, because ''her well-paying job depends on him being kept intact''.
** Even Timmy himself technically counts. He started off as a typical frustrated 10-year old, a bit of an outcast, and occasionally selfish. He always learned his lesson if he made a mistake, though, and only made wishes whenever they were issues crucial to his life. Then later he became more self-centered and wishing for stuff he wanted. Though season 6 and onward more or less reverted Timmy back to how he was in the first season.

* Franklin Turtle in a few of the later seasons of the ''[[Literature/{{Franklin}} original Franklin animation]]'', and ''[[Literature/{{Franklin}} Franklin and Friends]]''. When the show first started, Franklin was a WideEyedIdealist, and a BrattyHalfPint[=/=]{{Jerkass}} hybrid of sorts. After his CharacterDevelopment, he's pretty much a NiceGuy in season 5-6 of ''Literature/{{Franklin}}'', and all of ''[[Literature/{{Franklin}} Franklin and Friends]]'' save for a few [[SnapBack snap backs]] and [[AesopAmnesia aesop amnesias]] that unfortunately [[CharacterDerailment derail his character]] for an episode. He's [[CharacterRerailment back to being a nice guy]] by the next episode however.
* ''WesternAnimation/TomAndJerry'''s [[WesternAnimation/TomAndJerryTheMovie movie]] is mostly infamous due to having the titular duo (who are TheVoiceless and mortal enemies) talk, sing and ''be friends''.
** The Character Derailment actually happens within the movie itself, as Tom and Jerry spend the first ten minutes of the movie as their normal, mute, bitter enemy selves (though Tom ''does'' [[JerkWithAHeartOfGold save Jerry from the collapsing house]], it feels more like one of the EnemyMine moments they'd occasionally have in the original shorts), until Puggsy the dog convinces them to be friends. For about a minute, and their first bits of dialogue, they seem to cling desperately to their characterizations as enemies, as well as engaging in some admittedly pretty funny [[LampshadeHanging lampshading]] of the sudden shift:

** This goes back to 1975, when Hanna-Barbera rebooted Tom and Jerry for ABC Saturday mornings. They started out antagonistic in the first episode "No Way, Stowaways," only for them to shake hands at the end. As the series went on after two or three episodes of going at each other (without the old films' violence), they remained bosom buddies.
* Scott Summers/Cyclops on ''WesternAnimation/WolverineAndTheXMen2009''. In his origin episode Breakdown Cyclops, who has been depressed and ineffectual since losing his girlfriend Jean Grey, is revealed to have been extremely stupid and clumsy when he was first recruited to train as an X-Man. This apparently changed when Jean came into his life and "took the pain away" as Emma Frost, the rival love interest, put it. This is a big turn from the comics, where Cyclops was always a good, diligent X-Man, even as a student, where his primary problem was that he had weak social skills. This alternative characterization however embraces the stereotype that he is nothing without his long time girlfriend, while not showing anything suggesting he was ever a competent heroic leader.

** Ironically, the one sillier trait Grandad had from the off, that he would ''greatly'' exaggerate, or outright lie, about his role in the American Civil Rights movements (he once showed up late to a march because [[ItMakesSenseInContext he had to go get a raincoat]]), would also be submarined by later seasons. It turns out that Grandad was actually a member of the Freedom Riders, who rode busses into the Deep South to protest the southern state's discrimination against black people. While it only was he got on to the wrong bus by accident, early season Grandad would surely have been eager to brag about his role, conveniently omitting it was entirely unintentional.

** Seasons 16 and 17 were full of them. In "Flippity Francine" and "Francine Speaks Up" Francine is scared of attention despite loving attention and always wanting to be the star for the past 15 seasons. In "Read and Flumberghast" the entire third grade class is made way more gullible than ever. In "Opposites Distract" and "Prunella the Packrat" Arthur is a NeatFreak who throws everything he feels is old away, while in the older episodes he makes huge messes and is an extreme pack rat who won't even throw a popsicle stick away. The most extreme example is in "So Funny I Forgot to Laugh", where Arthur becomes a bully and Francine gets angry at him despite past episodes that revolve around bullying showing the bully (who is usually Francine) doing far worse things than what Arthur did. It also portrays Sue Ellen as someone unable to stand up for herself when Arthur bullies her, while in the first season she was the only student who could intimidate Binky.

** Their dynamic also derailed in some form due to the Urpneys decaying. In the first episode, the Urpneys were pitiful unwilling bumblers, but they and Zordrak were still effective enough to put the heroes in genuine mortal danger, allowing Rufus to [[TheWoobie come off as sympathetic]] against them. In most later episodes, they are [[HarmlessVillain completely ineffectual and doomed to failure from the start]], with the heroes gaining a smug awareness of this and [[UnscrupulousHero often taking fun out of tormenting the Urpneys]] just to ease the monotony of their routine schemes. In one episode, the Noops outright ''retreated in terror'' from the Urpneys because they had become too close an actual threat, nearing them more as self righteous {{Miles Gloriosus}}es who are only willing to bully harmless targets.
** At least some attempts were made to remedy both cases of Derailment throughout Season Three and Four, giving the Noops more {{Character Check}}s to their old personas and reverting them to competent but pragmatic heroes against the Urpneys (along with giving the villains a more [[NotSoHarmlessVillain Not So Harmless]] motive so that the heroes came off as genuinely defending themselves).

* ''Everyone'' in the ''WesternAnimation/WatershipDown'' [[TheSeries series adaption]]. For starters, Hazel is suddenly in love with Primrose after about two episodes, and Hyzenthlay was completely replaced altogether. Bigwig, in both the book and movie, was a bold, strong and knowledgeable fighter. Here he's turned into nothing more than a complainer and follower to Hazel, who doesn't know anything in war strategy. Pipkin, previously nervous, but extremely loyal, is turned into a CheerfulChild. Even [[HairRaisingHare Woundwort]] - the genocidal, slave-driving BigBad who eats hawks for breakfast and in the book contemplates how some day he hopes to meet a stoat so he can kill it - had a period in the series where he tried to ''stop the war with Watership Down and openly showed remorse'' for what he'd done. And the list goes on.

** Takua's friend Jaller, who goes from a serious and mature military leader-type to an almost childlike, somewhat insecure and shy-around-girls nerd. In the preceding story, he snapped at Toa Tahu when he was losing confidence in himself and [[BadassNormal defeated the extremely dangerous Pahrak-Kal by simply walking up to it and grabbing its power-giving Krana]]. In the movie, although still not a wimp, he doesn't showcase any of this militarist sternness, and simply lets Takua bail out of their mission.

* Quite possibly the character of Sheen from ''WesternAnimation/TheAdventuresOfJimmyNeutronBoyGenius'' and its SpinOff ''WesternAnimation/PlanetSheen''. In fact the ''derailment'' is due to the SpinOff. While Sheen could be insensitive and oblivious to to others, it was clear he cared about his friends and family in the ''Jimmy Neutron'' series. However, in ''Planet Sheen'', he is utterly indifferent his family and friends to the point where he doesn't even attempt to repair the damaged rocket to go back to Earth.

* While Lemongrab of ''WesternAnimation/AdventureTime'' was always a huge BaseBreakingCharacter, and even the staff of the show had different opinions of him, after his first appearance the show seemed to lean towards the idea that he wasn't truly evil, just really messed up. In his story in the third collection of character shorts, he seemingly devours his twin brother. In his next appearance, we see that he's become a tyrant who abuses his now maimed brother, and torments his lemon children when he had previously been portrayed as a loving parent. At the end of the episode, he fully eats his kinder brother, and loses any of the redeeming traits he may have had before. The next episode continues to show him keeping the lemon kingdom in misery, torturing his subjects for fun. He's ultimately torn apart, and then stitched back together, the characters suggesting that ''now'' maybe he'll be better. The only thing more sour than Lemongrab is the taste the whole thing left in his fans' mouths.

** To a lesser extent, Stan and Kyle becoming the [[OnlySaneMan Only Sane Men]] in the whole town is seen as this by some, with the main argument being that the characters have become [[WiseBeyondTheirYears far too wise and rational for nine year olds.]]

** Heloise. In Season 1, she was a MadScientist EnfantTerrible rightfully feared by everybody in Miseryville, for her cruelty and sadism surpassed even [[{{Satan}} Lucius]]. Sure, she had a sweet side when it came to her crush on Jimmy, but she was still an AxCrazy {{Yandere}} who would gleefully hurt Jimmy if he crossed her. Season 2's Heloise is the OnlySaneWoman almost solely defined by her crush on Jimmy with barely any of moments of ComedicSociopathy. Worse still, her status as TheDreaded who always had the last laugh was replaced with becoming the biggest ButtMonkey on the show and being treated as laughingstock by most characters, while her job as [[MegaCorp Misery Inc.]]'s top inventor (and one of Lucius' minions) was completely forgotten a few episodes into the season in favor of making her a generic GadgeteerGenius.

* Fauntleroy Fox from ''WesternAnimation/TheFoxAndTheCrow'' is usually portrayed as a suave, sophisticated, well spoken guy, while being naive and gullible about certain things is generally smart, for whatever reason in the last two Columbia cartoons "Tooth Or Consequences" and "Grape Nutty" he is portrayed as being fat and stupid, speaks in a deeper SimpletonVoice, and acts like a backwoods hick. [[CharacterRerailment He is back to being his usual self]] in the three UPA cartoons though.

* ''WesternAnimation/HarleyQuinn2019'': Dr. Psycho spent all of season 1 and the first half of season 2 as a JerkWithAHeartOfGold who was nowhere near as bad as his comic book counterpart and had genuine friendships with the crew. Season 2's second half derails him into a sadistic sociopath bent on world domination, turns him from the unscrupulous AntiVillain he was into a full fledged villain antagonist, and removes almost all of his redeeming traits. It's like they mixed up the one in the first season and first half of season two with the comic book version.

** Rhombulus seems to have suffered the worst amount of derailment over all the other members of the commission. He was depicted in his first appearance in season 2 as an impulsive but well-meaning ManChild with the mind of a 3 year old and a heart of gold who formed deep bonds with Lekmet and Star Butterfly. However, season 4 unceremoniously stripped him of all his positive qualities and threw them out the window to instead depict him as a brutal KnightTemplar monster-hating bigot who was willing to put lives in danger just to prove a point and rejoice to the act of genocide with a party.
*** If one stopped to think closely about Rhombulus, they would realize that he is actually 3 characters as the snakes he has for hands are shown to be sentient and have minds of their own. The snake hands were shown to act as voices of reason for Rhombulus in their first appearance but later episodes afterwards treated them both like voiceless sock puppets who would agree on everything Rhombulus did even on doing horrific acts.
** Heckapoo during season 2 was depicted as a strict and hard-working member of the commission who was in a deep and loving friendship with Marco for many years. However, during last two seasons, they showed her undergoing [[HeelFaceRevolvingDoor erratic morality changes and an inability to decide whose side she was on]], as well as a hypocritical BoomerangBigot with a huge case of FantasticRacism against monsters.

** Queen Moon was seriously derailed in the second half of season 4. Before that she was shown to be a strict but [[ReasonableAuthorityFigure level-headed and wise queen]] of Mewni who wanted what she believed was best for her daughter Star and the kingdom of Mewni. However she was revealed in the episode "Pizza Party" to having orchestrated a coup against Eclipsa by siding with The bigoted and insane Mina and creating a Solarrian army to accomplish this. This happened when Eclipsa already earned Moon’s trust at the end of season 3 and when it was already revealed that Queen Moon’s lineage were not really the rightful rulers of Mewni. Queen Moon did eventually get semi retailed at the end of the season but her last character arc was all about her attempting damage control after Mina double crosses her.
* ''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 turns 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 reveal 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.

* A chief complaint regarding the later ''WesternAnimation/WoodyWoodpecker'' cartoons (circa 1955 onwards) is that Woody is no longer an energetic, manic prankster, but instead a watered-down, generic hero character. [[ForgotFlandersCouldDoThat While the occasional short sometimes brought him back to his more manic roots]], they were few and far in-between.

** Some derailments have been taken a different way in the CGI series, either reversed back, exaggerated or taken a different way altogether. Skarloey is back to his more mature and no nonsense persona, while Edward is kind again, albeit [[ExtremeDoormat to a fault]], unable to say no to others and easily dissuaded from his work. Thomas interchanges between his older and newer persona to erratic extremes while Toby's meekness has reached [[WesternAnimation/MyLittlePonyFriendshipIsMagic Fluttershy]]/[[WesternAnimation/{{Rugrats}} Chuckie Finster]]/[[VideoGame/SuperMarioBros Luigi]] levels, being afraid of nearly anything that moves.

* ''WesternAnimation/AndyPanda'': In 1944, director Creator/ShamusCulhane wanted to try out a new, redesigned Andy that was a total {{Jerkass}} instead of a MickeyMouse-type [[TheEveryman everyman]]. The new Andy was hated by Creator/WalterLantz and audiences alike, and so he was dropped after just one cartoon, "The Painter and the Pointer", in which Andy threatened to kill his dog if the dog didn't pose for his painting, and to make sure he didn't move, Andy rigged a shotgun to shoot the dog if he moved from that position.

* Rick from WesternAnimation/RickAndMorty underwent a notable shift in the third season. Before that, Rick was more of a JerkWithAHeartOfGold who genuinely cared for his family deep down. He was also shown making mistakes and having trouble dealing with some situations, like turning the entire world in cronenbergs. Starting in season 3, he began being referred to as “The smartest man in the universe” by other characters. He became an InvincibleHero to the point where an entire army of other Ricks stood no chance against him. He also became far more belligerent to his family. In particular the bond he previously had with Morty was replaced with general animosity between the two.

** Madame Foster in the infamous Season 3 episode "Foster's Goes To Europe". Normally, she's the sweetest and coolest grandma ever and an absolute saint of a human being. Here, she ruins a European vacation which the gang planned to go on (and spent the entire episode struggling to get ready for) by stealing Mac's tickets at the very last minute. The episode ends with Madame Foster, her bowling buddies, and a homesick imaginary friend called Eurotrish going on the vacation instead, while Mac is [[ComedicSociopathy wrongly and unfairly]] blamed [[NoSympathy by everyone else]] for missing the trip. In the same exact episode, Madame Foster also [[MoralEventHorizon unties a group of defenseless imaginary balloons which sends them flying into the sky for no reason at all]].

* ''WesternAnimation/HarleyQuinn2019'': Dr. Psycho spent all of season 1 and the first half of season 2 as a JerkWithAHeartOfGold GrumpyBear who was nowhere near as bad as his comic book counterpart and had genuine friendships with the crew. Season 2's second half derails him into a sadistic sociopath bent on world domination, turns him from the unscrupulous AntiVillain he was into a full fledged villain antagonist, and removes almost all of his redeeming traits. It's like they mixed up the one in the first season and first half of season two with the comic book version.

** Lola Bunny was derailed from the ActionGirl she was in ''Film/SpaceJam'' to TheDitz in ''WesternAnimation/TheLooneyTunesShow'', but for many people, this ended up [[Administrivia/TropesAreTools being a significant improvement]] [[RescuedFromTheScrappyHeap over her previous characterization]].

** Sylvester goes from an IneffectualSympatheticVillain and a NobleDemon to, in the unreleased WesternAnimation/PepeLePew movie, a racist[[note]]he calls Pepé (who's French) a derogatory term for a Frenchperson and looks down on Europeans[[/note]] HateSink who gaslights Penelope.

** Madame Foster in the infamous Season 3 episode "Foster's Goes To Europe". Normally, she's the sweetest and coolest grandma ever and an absolute saint of a human being. Here, she ruins a European vacation which the gang planned to go on (and spent the entire episode struggling to get ready for) by stealing Mac's tickets at the very last minute. The episode ends with Madame Foster, her bowling buddies, and a homesick imaginary friend called Eurotrish going on the vacation instead, while Mac is [[ComedicSociopathy wrongly and unfairly]] [[NoSympathy blamed by everyone else]] for missing the trip. In the same exact episode, Madame Foster also [[MoralEventHorizon unties a group of defenseless imaginary balloons which sends them flying into the sky for no reason at all]].

* Even ignoring complaints about its quality as a CreatorDrivenSuccessor to ''WesternAnimation/TeenTitans'', ''WesternAnimation/TeenTitansGo'' begins representing its characters very inconsistently during the third season. Raven in particular goes from an introverted, intelligent, snarky girl with a violent streak to being [[TheDitz just as stupid]], happy-go-lucky, and fun-loving as Beast Boy and Cyborg. This starkly contrasts with the first two seasons in which Raven's intelligence compared to the other Titans was the focus of the episode.

* Even ignoring complaints about its quality as a SpiritualSuccessor to ''WesternAnimation/TeenTitans'', ''WesternAnimation/TeenTitansGo'' begins representing its characters very inconsistently during the third season. Raven in particular goes from an introverted, intelligent, snarky girl with a violent streak to being [[TheDitz just as stupid]], happy-go-lucky, and fun-loving as Beast Boy and Cyborg. This starkly contrasts with the first two seasons in which Raven's intelligence compared to the other Titans was the focus of the episode.

* Many of the characters in ''WesternAnimation/ThomasAndFriends'' have suffered from derailment... [[{{Pun}} thankfully not literally]].

* Pam in ''WesternAnimation/{{Archer}}'' became a completely different character as the series went on. Starting off as a pleasant but lonely and depressed HR rep, she turned into a sex-crazed, drug addicted complete loon. Though as always, Administrivia/TropesAreNotBad, as many fans enjoy this version of Pam ''much'' more.

** While the fanbase seems completely divided whether WesternAnimation/DaffyDuck's {{Flanderization}} during the 1950s from a bombastic {{Cloudcuckoolander}} into a {{Jerkass}} SmallNameBigEgo counts as derailment or [[CharacterDevelopment development]], most agree it crossed the line during the Creator/DepatieFrelengEnterprises era shorts, where he was evolved into a humorless, FauxAffablyEvil villain for WesternAnimation/SpeedyGonzales. One could take it as a double-sided coin, as pitting Speedy against a more conniving villain did at least allow him to come off as more sympathetic and fallible more often than [[InvincibleHero he did against Sylvester]], though it still would have been a swifter transition with a more fittingly-callous character.

* The Warden of ''WesternAnimation/{{Superjail}}'' losing his sadism after the pilot and gradually becoming more of an outright ManChild (as opposed to PsychopathicManchild) can be seen as this for some fans, although it's a highly contested example. He also he winds up no longer being someone to be feared, but instead be beat up and easily taken advantage of, and have his obliviousness and naivety cranked UpToEleven.

* ''WesternAnimation/TomAndJerry'''s [[WesternAnimation/TomAndJerryTheMovie movie]] is mostly infamous due to having the titular duo (who are TheVoiceless and mortal enemies) talk, ''sing and be friends''.

-->'''Tom/Jerry:''' You talked!!
-->'''Tom:''' Well, sure I talk! What do you think I am, a dummy?
-->'''Jerry:''' You said it, I didn't!
-->'''Tom:''' Ah, you little pipsqueak! I oughtta -- *pause* Hey! How come you never spoke before?!
-->'''Jerry:''' Well, there was nothing I wanted to say that I thought you'd understand... ''and there STILL isn't!''
** This goes back to 1975 when Hanna-Barbera rebooted Tom and Jerry for ABC Saturday mornings. They started out antagonistic in the first episode "No Way, Stowaways," only for them to shake hands at the end. As the series went on after two or three episodes of going at each other (without the old films' violence), they remained bosom buddies.

* ''WesternAnimation/TheSimpsons'' is a major offender: Homer going from a well-intentioned buffoon who was fundamentally a good person under his many flaws to to a hateful JerkAss who usually has little empathy for those around him, Marge going from a sensible, down-to-earth, and nurturing woman who was deeply supportive of her kids to a ditzy, snappy, and hypocritical housewife who has openly stated she would be much happier without her children, Bart going from an underachieving BrilliantButLazy prankster and troublemaker to a full-time [[TheSociopath sociopathic]] delinquent who can barely count to 10, and Lisa going from an idealistic ChildProdigy who was still just a little girl at heart to an ultra-liberal, activism-obsessed, egocentric, dramatic mini-teenager with little sympathy for those who go against her beliefs. And then there's Maggie, who's mostly a cute baby with a pacifier, but starting with "[[Recap/TheSimpsonsWhoShotMrBurns Who Shot Mr. Burns?]]", she exhibits a darker side in certain episodes (however, [[Administrivia/TropesAreTools many fans consider that one of the better cases of this trope, since Maggie]] TookALevelInBadass).
** Ned Flanders, when he first appeared, was a perfectly nice guy. He was religious and more than a little repressed, but he wasn't hurting anyone and [[FriendToAllLivingThings he seemed to love all people unconditionally]]. In fact, the whole joke was that Homer hated him for ''no'' reason. He was the kind of neighbor most people would be lucky to have, friendly, kind and always willing to lend you whatever you needed. Then came his {{Flanderization}}, where he went from a generally nice guy to his [[ExtremeDoormat ludicrously meek]], inoffensive, and Christianity-obsessed persona. The derailment kicked in later, when the Simpsons writers decided they wanted a Right-Wing Christian Strawman to mock and so they derailed Flanders to make him fit the bill.
*** And maybe this is more EarlyInstallmentWeirdness than character derailment, but in Flanders' very first appearance he was so thoroughly insensitive to Homer's obvious financial troubles that he came across as a complete Jerkass fully deserving of Homer's enmity (though Ned may not have been aware of just how bad Homer's financial problems were).
*** In fact, some recent episodes show that the derailment has effectively inverted the Ned-Homer dynamic, as now Homer is a happy-go-lucky idiot with Ned loathing him effectively just for existing. One episode actually covers this, in that Homer realized the reason he hated Ned was because he always found him better than him and moved on, while Ned's reasons to resent Homer in later seasons is that Homer keeps calling him Stupid Flanders within earshot of him and demeans him ''in front of Rod and Todd'', they do end up making amends, though.
** C. Montgomery Burns is a big victim of VillainDecay. In early seasons, Burns was a downright sadistic and evil old miser who generally treated his employees like crap, stole from children, tried to block out the sun (for money), violently mutilated sea animals to make Lil' Lisa Slurry and planned on turning a litter of puppies into a fur coat. Turn to later seasons and he's just a feeble old man who is more ineffectual than anything else and serves more as fodder for jokes about being behind the times then anything else. Although every now and then he gets a ForgotFlandersCouldDoThat moment and ends up doing plot such as launching his environmental hazards on the Amazonian forest or putting Mona Simpson on the run from justice out of spite.
** Patty and Selma have shown the most extreme case of derailment than anybody else. They were originally just a couple of gruff curmudgeons who hated Homer and think Marge should divorce Homer, take the kids with her, and remarry. Later seasons would add appalling housekeeping and near-criminal incompetence at their jobs (both arguably even worse than Homer's), not to mention smoking everywhere, including around children and on the job at the DMV (which nearly gets them fired -- until Homer takes the fall for the both of them). Selma would go through three astonishingly bad marriages (and she only wised up after realizing how long her last name was), while Patty became a full-fledged militant lesbian (despite that "Principal Charming" established that Patty is heterosexual and willingly celibate, while Selma has had celibacy thrust upon her and wants to have a husband and kids before she dies alone and unloved). Of course, all this pales next to becoming a new contender for Most Violent Simpsons Characters, being [[{{Flanderization}} utterly obsessed with trying to end Homer's marriage]], [[AndThereWasMuchRejoicing including celebrating his death by buying a tombstone for Marge]], [[MoralEventHorizon trying to kill him by pushing him off a bridge]] (though that was part of Homer's plot to land on the boat where his "Congratulations on Completing Community Service" party is being held, the fact that Patty and Selma were willing to kill Homer just because is unsettling) and attempting again later by reenacting the famous bathroom torture scene from the first ''Film/{{Saw|I}}'' movie.
** Moe is also worth a mention. When he first appeared, he was merely a surly and cynical bartender, who was a [[GrumpyBear pretty decent guy despite his rough edges]]. In later episodes, he's a miserable wretch and registered sex offender who conducts numerous illegal operations, tries to kill himself every other episode, and constantly lusts after women in revolting manners.
** Otto counts too. The character was originally depicted as a laidback youth who got along great with kids and was generally a really fun guy to be around, despite his humble status as a bus driver, his carefree nature, and the occasional hint that he was a pot smoker. Later on, he devolved into this wretched and dangerous lowlife with an insane addiction problem to any illegal and hazardous drug he can get his hands on -- a trait gets brought up every time he appears now and almost entirely defines his character in post-Golden Age seasons.
* ''WesternAnimation/FamilyGuy'':
** Stewie, previously a humorously sociopathic EnfantTerrible with matricidal tendencies, has become Brian's effeminate sidekick (the Doylist explanation was that the writers felt that they'd run the evil baby joke into the ground) though his violent tendencies do occasionally show up.
** Brian has changed from a [[DeadpanSnarker snarky]] intellectual ironically portrayed as vastly more intelligent than his owner Peter, to mainly a pretentious and egotistical douchebag, a preacher for the writers' liberal political views and TheChewToy concerning his inability to quit drinking, be a good writer, and hold a relationship.
** Lois, while at first as the down-to-earth one of the family, albeit with a somewhat healthy sexual appetite, has become an insane nymphomaniac and AbusiveParent. Being married to and living with a man like Peter for years could easily drive the most sane, sensible person crazy. One episode even implies this by showing a tumor in her brain after she mentions bottling up all the stress that Peter causes her.
** Meg has evolved from merely a unpopular high-school girl trying to fit in to an abused psycho of epic proportions.
** Peter himself, while always a bumbling idiot but with slightly good intentions (like Homer Simpson, only fatter, brasher, and more into pop culture from the 1970s and 1980s), has become a JerkAss PsychopathicManchild (making Homer Simpson look like the clueless, yet caring BumblingDad he was in the early days of ''The Simpsons'').
** Around Season 11, Chris TookALevelInJerkass just like his parents.
** Originally, Quagmire's obsession with women and sex didn't go farther than having a 50s swinger-type vibe, and was for the most part a happy-go-lucky CasanovaWannabe. He quickly became more successful in his pursuit of women, and eventually turned into an out-and-out ''rapist'' with a few offhand references to some of his conquests being ''underage girls''. He went through a second derailment in later episodes, with his intense (and randomly produced) hatred for Brian and SelfDeprecation based neuroses becoming the focus of a lot of his humor. He eventually became far more bitter and cynical even in scenes without Brian, as opposed to the more carefree, fun-loving person he used to be.
** Joe became overly macho to compensate for his handicap as opposed to his original character which was more like a good cop who happened to be crippled.
** Mort, originally just a SicklyNeuroticGeek, was reduced to a caricature of nearly every Jewish stereotype you could imagine ([[OutOfFocus despite not appearing much in the later episodes]]).
** There's something to be said for the character derailment of Cleveland Jr. for the run of ''The Cleveland Show'' how he used to be a hyperactive child to a fat and slow teenager (though considering that Cleveland, Jr. disappeared after he kicked around a golf ball like a soccer ball in "[[Recap/FamilyGuyS2E21ForeFather Fore Father]]", who knows what could have happened to him between "Fore Father" and his appearance on ''The Cleveland Show'''s pilot episode?). ''The Cleveland Show'' episode "A Rodent Like This" reveals that [[spoiler:the fat, weird, slow Cleveland Jr. is an impostor who killed the original and took his place and nobody noticed because they were too stupid]] though that may have been a simulation. Like most of the Griffin family he also TookALevelInJerkass during that show's final two and a half seasons.
** Cleveland himself became much louder and dumber on his spin-off ''WesternAnimation/TheClevelandShow''. If anything, [[{{Expy}} he just became Peter]] only blacker and slightly smarter.

* Numerous examples in the ''WesternAnimation/TotalDrama'' series, especially during ''Total Drama Action'', ''Total Drama World Tour'', and ''Total Drama All-Stars''.
** Trent. In ''Total Drama Island'', he was "the Cool Guy" and the closest thing to a normal teenager: friendly, easygoing, grounded, humble, and talented. He developed a thing for Gwen and they end up going out on the last episode. By the fifth episode of TDA, his relationship with Gwen has turned him into a clingy, neurotic, and desperate loser who '''has''' to please her since he's so worried about her feelings dwindling since she has more in common with Duncan. It gets so bad that he starts throwing challenges for her and Gwen has to convince his team to boot him off. And that's not even getting into [[CompressedVice his sudden]] maniacal SuperOCD obsession with the number "9".
** Geoff and Bridgette both completely lost their personalities in TDA and TDWT. Their relationship transformed from ordinary teenage lovers with a supportive emotional connection to each other and many major friendships with other contestants to being excessively physical and hormonal MakeoutKids who spend the other half of their time bickering with each other and were basically {{Satellite Character}}s to each other (little wonder the popularity of the "[[PortmanteauCoupleName Gidgette]]" ship massively declined after TDI). Geoff then TookALevelInJerkass on the Aftermath segments and turned from a laidback, fun-loving NiceGuy into a sadistic, narcissistic SmallNameBigEgo who loves torturing his fellow contestants, obssesses over his appearance, only cares about fame and money, and generally keeps failing Bridgette as a boyfriend. Meanwhile, Bridgette was derailed from a compassionate, sensible, easygoing, and tomboyish GranolaGirl to a shallow, bitchy, hypocritical, and nymphomaniacal ClingyJealousGirl who violently beats up Geoff for looking at other girls or insinuating she's fat, breaks down when she realizes her boyfriend won't be in TDWT with her, becomes completely smitten by [[LatinLover Alejandro]] and tries to kiss him on national TV, and generally cannot survive for 5 minutes without satisfying her physical and emotional needs for big, strong, handsome men.
** In TDA, Courtney went from an uptight and bossy but well-mannered and well-meaning GoodCounterpart to [[AlphaBitch Heather]] who had a sense of honor in playing the game to a violent, spoiled, manipulative, and cutthroat {{Jerkass}} who sues if she doesn't get what she wants (something she only did once in TDI, in a justifiable case) and cares only about what she wants, becoming pretty much as bad - or worse - than Heather was. And then things got worse after Duncan cheated on her with Gwen in TDWT (done solely to [[ShipSinking kill DuncanXCourtney]] and make then-FanPreferredCouple [=DuncanXGwen=] canon). Being furious and upset over the incident at hand is one thing (and completely understandable), but actually ''losing challenges on purpose'' for no reason other than to spite Gwen is worse.\\\
Things just get worse for Courtney in TDAS. At first it appeared as if the writers [[CharacterRerailment were finally trying to get Courtney's character back on track.]] After the whole Duncan incident, Courtney finally became Gwen's friend again and the two were just as close as ever, and [[OppositesAttract she even pursued a new romance with Scott.]] It looked as though Courtney finally had a chance to be likable again. All that development was suddenly derailed in ''one entire episode''. Out of nowhere, Courtney reveals that she has already planned out what she's going to do now that she's in the final five and what order she plans on getting rid of the other contestants, two of whom are her close friend and new love interest. She chooses to backstab them because a million dollars is worth more than her relationships with either of them apparently.
** Happens to Gwen in TDWT, where she goes from a moody but loyal and kind-natured MisunderstoodLonerWithAHeartOfGold to being an selfish, unrepentant, and manipulative {{jerkass}}. She kisses Duncan while he was still with Courtney. She feels some remorse for doing it at first but when the kiss is found out, she doesn't try to vote herself out like the last season or apologize. And later she manipulates Cody's feelings for her to vote Courtney off. She's even lampshaded as being "New Heather".\\\
It only got worse for Gwen in TDAS, with many seeing her as having become "too girly" and too concerned with what other people thought of her (such as giddily gushing with Courtney about each other's hair and clothes), as well as her handling of [[YoYoPlotPoint her second fallout]] with Courtney, which made her out into a {{hypocrite}} for treating Courtney the exact same way she had been treating her in TDWT. It should be no surprise at this point that she has gone from one of the show's most universally loved characters to one of its most divisive.
** Leshawna, most definitely. TDI had her as a girl who would [[SassyBlackGirl take crap from nobody and could get quite feisty]], but was still very kind, loyal, caring, and friendly, to the point where her "elimination" came in part because everybody who had been eliminated at that point liked her so much. Then comes TDA, where, for absolutely no good reason she manipulates her teammates into giving her a reward by pretending to cry and being sentimental, only to trash-talk them behind their backs. It's even worse in TDWT, in which she's now a massively arrogant {{jerkass}} and a gargantuan {{hypocrite}} with little to no redeeming qualities, and goes right back to hating Heather even after supposedly making up with her in TDA; even beating Heather up when Heather is trying to warn her about Alejandro's villainy and, after learning that she was right, ''is still proud of doing it''. Basically, much like Courtney, she went from being Heather's moral and ethical superior to being just as bad as her in every way (in fact worse, due to Heather's CharacterDevelopment around the same time to a minor JerkWithAHeartOfGold).
** DJ too. He was introduced as a sensitive, kindhearted, and easygoing LovableJock who was capable of being brave, tough, and even mischievous or playful [[CowardlyLion when the time called for it]] (like overcoming his fear of water to help his team win a challenge, standing up to Chef for forcing him into an illegal alliance, and joking around with Geoff and Duncan). But in TDWT, he's become a gigantic crybaby who ScreamsLikeALittleGirl at virtually everything, constantly cries and blubbers for his mother (something he never did once in TDI), and is completely useless in challenges due to being such a cowardly wimp that he can't concentrate on anything except his own fearfulness.
** Ezekiel's case in TDWT is one of the most infamous in the show's history. Originally a meek and clueless homeschooler who got eliminated for [[InnocentlyInsensitive making several unintentionally sexist remarks]], he quickly became an EnsembleDarkhorse. In response to fan demand to give him a second chance, the writers brought him back, but he was turned into a SmallNameBigEgo {{Determinator}} and an obnoxious {{Jerkass}} as some sort of CreatorBacklash to his unexpected popularity. After losing the first challenge for his team and being voted off, he decided to stow away in the ship's cargo hold, which eventually resulted in him mutating into a feral, barely-sapient [[Film/TheLordOfTheRings Gollum]] {{Expy}} with almost no trace of the naive and innocent farmboy he once was left in him.
** Duncan also qualifies because during his return in TDWT, he went from a carefree JerkWithAHeartOfGold who actually did have some degree of moral standards to a remorseless asshole with no redeeming qualities who would stoop to any level to be bad. Throughout the season, he holds the ConflictBall, cheats on Courtney with Gwen (while in ''Island'' he voted for Trent for supposedly cheating on Gwen with Heather), never helps his team, cheats during the game, treats almost everyone like crap (especially Courtney), becomes a ManipulativeBastard, and helps [[BigBad Alejandro]] stir the pot for no good reason. It's no wonder he went from being one of the show's most beloved characters to one of its most controversial as a result of the season.
** Owen also counts. He started out as an extremely friendly big lovable oaf who was willing to try anything in the name of fun, up to and including dating the AxCrazy Izzy. Suddenly in TDA, he becomes a self-centered SmallNameBigEgo and an obnoxiously moronic {{Jerkass}} who can't stop himself from eating for one second and doesn't care in the slightest when his actions harm others, while in TDWT, he decides out of nowhere that he wants to break up with Izzy for being crazy despite having been totally infatuated with her insanity for the previous two seasons.
** Lindsay was set to [[TookALevelInBadass to grow leadership skills and develop some brainpower]] in TDA, but that was suddenly thrown out of the window with her elimination (in which ''she voted herself off by accident'') and never revisited afterwards. And then she ends up getting dumber and dumber with every season, voting for herself near-constantly in TDWT and being unable to understand simple concepts like pushing and pulling in TDAS.
** Like all of his team that season, Harold was hit by this in TDWT. In the previous 2 seasons, he was a well-meaning and intelligent CrouchingMoronHiddenBadass whose "mad skills" rescued his team on more than one occasion, thus proving himself a good teammate whose boasts were almost never empty. Suddenly, in TDWT, he's become an unbelievably arrogant SmallNameBigEgo and KnowNothingKnowItAll who does nothing worthwhile to help his team in challenges (unless constantly prattling on about himself and his "knowledge" is considered something) and whose only contribution is being hit with the IdiotBall and getting convinced by Alejandro to perform a StupidSacrifice.
** Cody. Presented in TDI as a cheerful and well-meaning DoggedNiceGuy who ultimately decided IWantMyBelovedToBeHappy (and in fact played a major role in helping Gwen hook up with Trent), he TookALevelInJerkass in TDWT and transformed into a desperate and hypocritical StalkerWithACrush with SingleTargetSexuality towards Gwen who will do anything to make her like him without caring in the slightest about anyone else or even the challenges at hand. Small wonder he transformed from an EnsembleDarkhorse to a BaseBreakingCharacter as a result of the season.
** From the cast of ''Revenge of the Island'', we have Zoey and Cameron, thanks to their friend (well, boyfriend in Zoey's case) Mike and his SuperpoweredEvilSide Mal. Zoey went from a grounded but somewhat gullible girl who was [[BewareTheNiceOnes able to stand up to herself when needed]] to being completely helpless to the point of needing Mike to help her win challenges (despite keeping the skills and abilities she had developed) and being TooDumbToLive by completely unable to recognize that Mike was actually Mal despite being warned by three different people that Mike was NotHimself (to the point where she actually thought Alejandro was warning her about ''Courtney'' in one episode) and being aware of his [[SplitPersonalities DID]] from the previous season. Cameron, despite being established in his debut as one of the show's most intelligent characters bordering on ImpossibleGenius, stupidly trusted Mike when he was Mal, somehow failing to recognize some of the very obvious signs something was wrong with his friend even though he was one of the first to discover Mike's mental disorder in the previous season.
** Dave from the cast of ''Pahkitew Island'' is a very extreme case as he was derailed '''in the very season he debuted in'''. At the beginning of the season, he was established as a pessimistic and neurotic DeadpanSnarker OnlySaneMan who also happened to have a crush on the friendly and grounded PassionateSportsGirl Sky. But around the 6th or 7th episode he's completely lost all his other traits to focus solely on his crush on Sky, as he started becoming too dependent on her which led to him suffering from an emotional breakdown when [[spoiler:she and Max switched teams]] and ultimately [[spoiler:voting himself off]] in the 9th episode when she rejected him (albeit rudely due to being in a bad mood at the time), leaving him a bawling wreck and beginning a SanitySlippage. Things got even worse in the finale when he completely loses his mind after learning that the reason why Sky rejected him was because [[spoiler:she already had a boyfriend back home (who she tried to break up with prior to joining the show)]], conducts a huge FaceHeelTurn, and abruptly becomes the FinalBoss of the season in order to thwart her chances of winning the million (and actually [[TheBadGuyWins succeeds in one ending]]).

* Cosmo in ''WesternAnimation/TheFairlyOddparents'' got this. It was established in the first season that he ''ran away'' from home to marry Wanda. In another episode he broke down crying from having to be away from her overnight. It was very clear they enjoyed their relationship. Then, suddenly, in seasons four and five he was drooling over every attractive woman that came onscreen, repeatedly calling Wanda a nag and more, and acting like she had BoundAndGagged him at the altar. Hell, the original ''Oh Yeah! Cartoons'' shorts of ''Fairly [=OddParents=]'' had him be a lot different. Compare the calm, deeper-voiced Cosmo who was Wanda's equal intelligence-wise and actually seemed to share a loving relationship with his wife. Now, compare that to the sociopathic ManChild with the screechy voice portrayed in the Fairly Odd Parents series and see how far he fell. It's rather handy, you can tell his intellect by his voice pitch. Deep/slightly high voice, reasonable degree of smarts, really high voice, no smarts.
%%** Wanda was initially as stupid as Cosmo, and even happily admitted to, along with Cosmo, being "two halves of a whole idiot" in an episode. Later on, however, she became smart, with Cosmo being just one whole idiot.

* In almost a reversal of the aforementioned Bloo example, Rufus and Amberley of ''WesternAnimation/TheDreamstone'', despite always being cutesy and cheery protagonists in contrast to their enemies, had some visible cynical traits and flaws in their own right in the pilot (Rufus was a CloudCuckooLander BadassAdorable while Amberley was a [[BrattyHalfPint moody tempered]] but thoroughly helpful [[VitriolicBestBuds Vitriolic Best Bud]]) and had almost an equal focus in sympathetic spotlight and humor as the villains. In the majority of later episodes, the two became [[TastesLikeDiabetes ridiculously juvenile]] and [[TheLoad ineffectual]], to the point their interaction was often extremely uneventful until [[VillainProtagonist the Urpneys]] attacked them every episode.

* In Hyperion Studios' TV series of ''WesternAnimation/TheItsyBitsySpider'' (1994-96, based on their short subject which played with the feature ''Bebe's Kids''), Leslie was a sweet, introverted {{meganekko}} in the first season. In season two, she became rather abrasive to her schoolmates and friends, showing occasional signs of emotion.

** Meg has evolved from merely a unpopular high-school girl trying to fit in to an abused, suicidal psycho of epic proportions.

** Happens to Gwen in TDWT, where she goes from a moody but loyal and kind-natured MisunderstoodLonerWithAHeartOfGold to being an selfish, unrepentant, and manipulative {{jerkass}}. She does an example of MoralDissonance by kissing Duncan while he was still with Courtney. She feels some remorse for doing it at first but when the kiss is found out, she doesn't try to vote herself out like the last season or apologize. And later she manipulates Cody's feelings for her to vote Courtney off. She's even lampshaded as being "New Heather".\\\

to be an EvilAllAlong tyrannical dictator who wanted to conquer many worlds and created armies of robots to do so.

* ''WesternAnimation/Amphibia'': King Andrais Leviathan was introduced in his debut in season 2 as a goofy and fun loving king who had a disregard for sophistication and often carried around and used pink women’s sunglasses. However the season 2 episode “True Colors” suddenly revealed him to be an EvilAllAlong tyrannical dictator who wanted to conquer many worlds and created armies of robots to do so.