History CharacterDerailment / AnimeAndManga

*** There is a smaller group that suggests Ash's biggest regression was not Unova but rather Alola. As while he was more competent than he was in ''Best Wishes'' [[spoiler:with Ash '''finally''' winning a Pokémon League]] it's been observed his '''maturity''' seemed to be at a low not seen since Kanto. In ''[[Anime/PokemonTheSeriesSunAndMoon Sun & Moon]]'', Ash spends very little time training, often being treated as a ButtMonkey getting into trouble, and many instances of irresponsibility like trying to cheat on an exam. It's also been argued the idea that Ash would ever want to go to School rather than travel is completely antithetical to his character (which is supported by the alternate universe ''Anime/PokemonIChooseYou'' which suggests Ash's greatest fear is having to go to school).

** Cassidy and Butch while initially popular characters being serious foils to Jessie and James fell into this after a severe case of VillainDecay and {{Flanderization}} in ''Anime/PokemonChronicles''. In this series of side stories, the two strong schemers became copies of Jessie and James without any of the HiddenDepths that made the two popular, to begin with. "Training Daze" in particular hurt their image as being a FullEpisodeFlashback it retroactively made them '''always''' inferior to Jessie and James, which was the exact opposite of their original intent. This derailment would carry over to the main series, and its poor reception might be why the duo made no appearances from Gens V-VII. When the duo finally returned in ''Anime/PokemonJourneys'', it was revealed that they had quit Team Rocket and began an honest living which can either be seen as rerailment for regaining competence or further derailment for giving up their evil ambitions.

*** Possibly the most egregious example is in his Gym battle against Elesa. He spends hours prior to the battle trying to prepare a strategy for her, only to come up with something completely idiotic: benching his ''entire team'' in favor of his inexperienced Palpitoad, expecting to sweep her clean with just one Pokémon. In the end, he chooses to '''disregard strategy entirely''' and just rely purely on Pikachu, [[BrokenAesop not considering that the strategy itself might have just been terrible]].

** In the middle of ''[[Anime/PokemonTheSeriesDiamondAndPearl Diamond & Pearl]]'', Ambipom is literally PutOnABus for incredibly contrived reasons that make no sense given the Pokémon's previously established character. From the beginning Aipom/Ambipom was shown to love Contests, which eventually led to her getting traded to Dawn, the Contest Coordinator of the group. [=DP124=] has the characters participating in [[MundaneUtility Pokémon Ping Pong,]] and Ambipom suddenly decides to leave her trainer and the Contests she loved so much to go off with a complete stranger and train for an activity she didn't even know existed before the previous episode.
** Ash's Pikachu started out as bratty and self-centered but over time received character development to become a natural leader, who acted as a mediator to other Pokémon and had full loyalty to Ash. A common plot of Pikachu shorts (and the occasional filler episode) would be Pikachu being left in charge while the humans were away and struggling to control the chaos caused by the other Pokémon. Come ''Sun & Moon'' and Pikachu began to regress to how he was in Kanto becoming more selfish, rebellious, and mischievous, often ignoring Ash's orders and even attacking him for fun on occasion. If anything Pikachu became the most mischief-prone of Ash's Alola team and acted more like a child than a leader. This regression sadly progressed to ''Journies'' and became even worse. In episode 30 Pikachu was willing to run away from Ash all because he was spending time with Riolu. A Pokémon is a baby which by nature requires extra attention. Pikachu understood this with Phanpy, Larvitar, Scraggy, and Noibat. Yet, suddenly Pikachu believes Ash no longer loves him. To add salt to the wound when Ash apologizes Pikachu accepts the apology... only after electrocuting Ash.

** Ash's Charmander, upon evolution into Charmeleon, goes from arguably the nicest of Ash's Kanto starters to volatile and uncontrollable. Upon evolution into Charizard, it becomes a complete {{Jerkass}} that rarely even tolerates Ash until halfway through the Orange Islands arc when Ash saves its life (again). While Charizard's behavior was intended to teach Ash some humility, it still comes completely out of nowhere and is treated entirely as Ash's fault, [[InformedWrongness even though he]] ''[[InformedWrongness had]]'' [[InformedWrongness tried controlling it before and Charizard actively refused to cooperate]].

* The [[DownerEnding ending]] for ''Manga/AttackOnTitan'' was controversial due to Eren's characterization taking a full 180. Beforehand, he was a sympathetic WoobieDestroyerOfWorlds who was willing to do whatever it takes for the sake of freedom for his people and avenging his mother's death. However in the final chapters it's revealed that through the TimeyWimeyBall he was ''directly responsible'' for his mother's death BecauseDestinySaysSo, erasing all his motivations and convictions, making him into a {{hypocrite}} and the TheReasonYouSuckSpeech he gave Reiner completely meaningless.

* In ''Manga/{{Bleach}}'' Uryu seemingly has forgotten about how Mayuri tortured his grandfather to death. Instead of displaying open hatred for Mayuri when they meet up again, he only seems mildly annoyed with Mayuri, and his reaction is PlayedForLaughs. The show seems to be glossing over the first time they met and what Mayuri did to his grandfather and his entire clan. Sure, Uryu in the second meeting wasn't in a position to ''do anything'' about his hatred of Mayuri, being too badly injured to even stand up, but if anything that should make him him even ''angrier''.

* Priss Asagiri falls victim to this in the final episodes of ''Anime/BubblegumCrisis Tokyo 2040.'' She reveals to her love interest, ADP Officer Leon [=McNichol=], that the real reason she hated the AD Police was that they broke her favorite CD during a boomer attack. Before then, she was developed as a complex, mysterious, stoic loner. This revelation derails her integrity for the sake of cheap laughs and misguided social commentary.
* [[LightNovel/ACertainMagicalIndex Kuroko]] [[Manga/ACertainScientificRailgun Shirai]] [[ZigZaggedTrope zig zags]] this. In regular plots (Both for ''Index'' and ''Railgun''), she's shown as a competent member of Judgment and a ReasonableAuthorityFigure that just happens to have a crush on a girl, which is PlayedForLaughs but is hardly the only thing she does. In [[{{filler}} anime-only stories]], she suffers from full-blown CharacterExaggeration, becoming a full-blown PsychoLesbian who's willing to resort to drugs to get Mikoto (which she thankfully fails at).

* A case can be made for more than a few of the characters of ''Anime/CodeGeass'', but none more so than [[TheEveryman Ohgi]], initially the voice of reason of the rank-and-file Black Knights who understood the burden of leadership that rested upon Zero, he [[LoveMakesYouDumb lost the plot once he fell for Villetta]] and made many questionable decisions, with ultimately disastrous results. The CompilationMovie series [[AuthorsSavingThrow most likely tried to give him some]] CharacterRerailment by actually attempting to be more reasonable with said decisions, [[InSpiteOfANail which simply didn't affect how everything still went down]].

* Siesta from ''LightNovel/TheFamiliarOfZero'' is a gentle and sweet {{meido}} in the first season, but in the next two she borders on BeAWhoreToGetYourMan, with no logic or explanation.
* Franchise/{{Gundam}}

** ''[[Anime/MobileSuitGundamAGE Gundam AGE]]'' gives us Zeheart Galette. For most of the show he's a NobleDemon who makes a point of remembering his fallen comrades and subordinates and fights for every Vagan to return to the "Eden" that is Earth. After [[spoiler:Ezelcant reveals his true, SocialDarwinist agenda--the one that had him killing his own citizens--Zeheart devotes himself to it after about thirty seconds of hesitation. By the end, he's willing to throw away the lives of his most loyal aides for the sake of a diversion and wipe out multiple {{Mook}}s into the bargain]]. The OVA ''Memories of Eden'' [[AuthorsSavingThrow explained this]] when he admits [[spoiler:he objected to Ezelcant's true plan, but went through with it since [[SunkCostFallacy those who died under his command would have done so for nothing otherwise]]. It's implied his failure to reconcile these two mindsets led to his subsequent VillainousBreakdown]].

* Dumas from ''Anime/{{Kiba}}'' starts off as the strong, quiet champion of Tempura/Templer, then [[spoiler: makes a shocking FaceHeelTurn and would have lead Jimoto's invaders to overtake Tempura had not Zed's Spirit gone on a rampage and stopped them.]] The really interesting part was that Duma's reasons for this were pretty reasonable: because of his family history, he basically wanted to shape his own destiny. However, after Zed’s Spirit rejected him, which took a toll on his sanity, [[spoiler: he became a regular psychotic baddie whose sole purpose in life was betraying Tempura in every way possible and becoming royalty.]]
* In the ''Manga/KOn'' [[TheMovie movie]], Azusa becomes quite upset about the idea that Yui might have romantic feelings for her. Quite a few fans thought this was odd. Azusa might get exasperated by Yui's antics at times in the manga, but it was clear she wasn't against Yui's affection for her ''in principle'', and in the end, even got very close to confessing her feelings to Yui ''herself''. From the other perspective, it can also be seen as derailing Yui from a simple CuddleBug to someone who uncomfortably won't take no for an answer.
* The last few episodes of ''Anime/LeChevalierDEon'' do this with Robin. He goes from being friends with and saving D'eon's life to indifferent and willing to fight him, while instead teaming up with the main villain for the series. They tried to write in reason for it... but just didn't sell it very well.
* Kanade and Usami are both getting hit by this on ''LightNovel/MayoChiki''. Kanade is going from a sexually dominant, but playful and overall nice girl to a {{jerkass}} {{troll}} that has no problem on causing property damage and intimidating others with her BattleButler. Usami went from a nice {{tsundere}} to a generic angry tsundere, overlapping with CharacterExaggeration. Kanade eventually gets better, Usami.... is DemotedToExtra so nobody knows.

* The infamous island/Africa arc in ''Anime/NadiaTheSecretOfBlueWater'' is notorious for distorting the characters' personalities and relationships with each other. Nadia herself suffers from this the most. While she is a troubled character in the central plot of the story, the filler arc changes her personality from a NotGoodWithPeople sort of character to a [[JerkAss totally unlikable, selfish, psychotic, cartoonish buffoon]]. It is hard not to watch any of these episodes without noticing how many times the writers press "reset" on the characters' personalities and relationships with each other. (The Lincoln Island and Africa arcs are especially insulting, for [[AssPull sidestories that feel very out of place with the main story arc, not to mention poorly thought out]].)

** During his first appearance Obito Uchiha was a guy who strongly believed in ThePowerOfFriendship and could be the potential WhiteSheep of the Uchiha, but after TheReveal he turns out to be Tobi, a ruthless villain who wants to throw the world into despair and isn't afraid to threaten and harm newborns. And all because Rin died, which was perceived by some as a poorly-executed FreudianExcuse.

* One of the big problems that people have pertaining to the last couple volumes of ''Manga/NegimaMagisterNegiMagi'' has to do with one of its final storylines, the Sports Festival arc. The arc, which involves [[spoiler: cheerlearder Misa convincing most of Class 3-A that Negi is a philanderer (despite the fact that he's just a kid with no real concept of romance and that most of the escapades involving that were forced upon him by his students) and that they should use the final event of the school's Sports Festival to teach him a lesson about being a womanizer]], took most of the character development that happened in the past 343 chapters (and some elements from early in ''the first chapter of the arc'') and basically threw it out the window for the sake of story that basically incorporates the ComedicSociopathy aspect of Ken Akamatsu's previous work, ''Manga/LoveHina''. Even those students that should know better, like Setsuna and Kaede, windd up acting out of character in this arc and side with the rest of the class in terms of causing trouble for their teacher. It also doesn't help that the climax of the story involves [[spoiler: the students basically raping Negi by sticking Chizuru's spring onion Pactio item up his butt, with Nodoka and Yue finally having enough of this crap to come to his aide]].

* In ''Anime/PuellaMagiMadokaMagica'', Kyosuke Kamijou (Sayaka's ChildhoodFriend love interest, who seems to think his relationship with her as strictly platonic) and Hitomi Shizuki (one of Sayaka's friends and TheRival for Kyosuke's heart) inadvertently [[spoiler:send Sayaka on her StartOfDarkness]]. However, their actions in the anime [[HumansAreFlawed are somewhat understandable]] and they try to give Sayaka a chance (e.g. Hitomi tells Sayaka to face her feelings and gives her a day to confess to Kamijou). Both Hitomi and Kyosuke were unaware of all the problems that Sayaka had [[spoiler: such as Sayaka finding out that her soul got ripped out of her body and put into a SoulJar because no one tells Hitomi and Kyusuke anything. After Sayaka's death, it is revealed that Hitomi fell into depression and thinks [[ItsAllMyFault it's all her fault]] while Kamijou also seems to miss Sayaka.]] Unfortunately, these shades of gray are all dumped in the PSP game. In a certain route in the game [[spoiler:[[RonTheDeathEater Hitomi becomes a full-on]] [[AlphaBitch Alpha]] BitchInSheepsClothing, while when Sayaka starts decomposing due to her distance from her Soul Gem Kyosuke calls her "a disgusting (understandable) ''monster'' (not so much)", then [[KickTheDog twists the knife further]] by adding "Shizuki is the only one I need!"]] Ouch. However, the outcome of this game does depend on how you play it, so there are some scenarios where Hitomi and Kyosuke don't get character derailment (including a route where Sayaka ultimately gets happiness with Kyosuke).

* Kaede Fuyou from the anime ''VisualNovel/{{Shuffle}}'' Is best known for going {{Yandere}} when the male lead chose another girl over her. If you described this to someone who had only read the VisualNovel that the series is based on, they would be ''very'' confused, since her behavior during the exact same situation in the game was [[TearJerker about as far from 'Yandere']] [[IWantMyBelovedToBeHappy as it is possible to get]].

* ''Anime/TenchiMuyo'''s Mrs. Masaki. From Tenchi's point of view, his mother was this kindhearted woman and it was incredibly possible that Ryoko knew this, too. This characterization would carry over into ''Anime/TenchiUniverse'' and brief moments of ''Anime/TenchiInTokyo'' under her "Achika" name. Flash forward about six-seven years with the new [[OriginalVideoAnimation OVAs]] and we find out that [[spoiler:Tenchi's mother, Kiyone, wasn't a kindhearted woman, but a total prankster who even treated her ''death'' as a joke and that the true kindhearted woman was Noboyuki's secretary Rea.]] Not only were fans pissed off, but so was Tenchi.
** There's also Mihoshi, who suddenly loss a massive amount of IQ points between the second OVA series and the third, becoming just as dumb as her alternate universe counterparts.
* In ''Franchise/TransformersGeneration1'', Cyclonus and Scourge were a pair of dangerous, cunning, devious warriors. In ''Anime/TransformersHeadmasters'', they suddenly became a pair of bumbling idiots who kept getting in Sixshot's way, and wondered why Soundblaster lost all respect for them. They were quietly dropped from the show soon after.

* This occurred in ''LightNovel/{{Tytania}}'', and it happened to, of all people, Estrades- the man turns from a calm, devious schemer who was perfectly fine being ordered about by his brother Ajman to a wild, rabid, hateful person who despised his sibling with every fiber of his being. To top it off, his derailment is combined with a severe case of a mixture of the IdiotBall and TooDumbToLive when [[spoiler: he offs himself by shooting himself after tumbling down a flight of stairs.]]
* In ''Manga/YamadaKunAndTheSevenWitches'', Nene Odagiri is initially, when she actually befriends Yamada and stops just being a [[DropInCharacter drop-in]], incredibly loyal and self-sacrifing towards him, not only [[IWantMyBelovedToBeHappy wanting him to be happy despite her own infatuation]], but also going out of her way to ensure he becomes happy. Not that she stops being impolite and hot-tempered - a HiddenHeartOfGold should remain hidden in her eyes - but she is AFriendInNeed, and he comes to consider her so. When the problem is solved, and Yamada gets together with the girl he loves - Shiraishi - she becomes much more mean-spirited. Odagiri has now suddenly forgotten that she wanted him to be happy and tries to steal Yamada away from Shiraishi. She still helps him out when he needs her, but usually only does it with the intention of having her notice him, and she will pull every trick in the book to convince him that he should rather associate with her than Shiraishi.

** Happens to Kaiba throughout the series to a lesser extent both canonically and once more due to dub-based exaggerations of character, as he continually forgot lessons about teamwork...though that is more caused by the series' original writer continuously railroading Kaiba into the role of antagonist rival to Yami Yugi even past the point where they'd settled their issues.
* Daichi Misawa of ''Anime/YuGiOhGX'', whose TeenGenius personality became grotesquely twisted out of shape until he began acting directly contrary to what had previously been shown. (Then again, a drastic personality change is {{justified| Trope}} if he really was [[EpilepticTrees raped by a love-crazed Amazon]].) He eventually snaps/has an epiphany and runs naked through the school grounds a la Archimedes, and then gets PutOnABus. He eventually returns but does little before deciding to live in another dimension with said love-crazed Amazon. This was arguably a minor attempt to return his character to its roots as he made this decision partly because he felt more appreciated in the other dimension than he did in his native one and acceptance/recognition was what he had sought from the start.

* ''Anime/YugiohVRAINS'': GO Onizuka goes from being Playmaker's hot-blooded, prideful, but good-natured rival who loves to entertain the crowds in the first season to the second making him a power-hungry jerkass who's single-mindedly obsessed with gaining strength and avenging his losses at Playmaker's hands. Explicable due to Vrains not having a consistent writing staff.

* Daichi Misawa of ''Anime/YuGiOhGX'', whose TeenGenius personality became grotesquely twisted out of shape until he began acting directly contrary to what had previously been shown. (Then again, a drastic personality change is {{justified| Trope}} if he really was [[EpilepticTrees raped by a love-crazed Amazon]].) He eventually snaps/has an epiphany and runs naked through the school grounds a la Archimedes, and then gets PutOnABus. He eventually returns but does little before deciding to live in another dimension with said love-crazed Amazon. This was arguably a minor attempt to return his character to its roots as he made this decision partly because he felt more appreciated in the other dimension than he did in his native one and acceptance/recognition was what he had sought from the start.
* ''Anime/YuGiOh'':
** For a good number of people this happened in Season 4 of the anime, to Yami Yugi. He freaks out when nearly losing a duel despite having far developed out of this trait as per the manga, and is goaded by his opponent into playing a card that would make him go against his (or rather, Yugi's) value system. Unfortunately however, this is heavily a result of 4Kid's dub-based changes in characterization compounding a recurring error about Yami Yugi taking things too far when pushed, which the series HAD been trying to call out at the time as it hadn't been addressed since Yami Yugi almost killed Kaiba in Duelist Kingdom and Creator Kazuki Takahashi admitted himself had forgotten to deal with, but had left to the season to do so.
** Mai in Season 4, when she [[FaceHeelTurn joins the bad guys briefly]] and all her characterisation appears lost. Creator/LittleKuriboh of [[WebVideo/YuGiOhTheAbridgedSeries Yu-gi-oh! Abridged]] even lampshaded at one point that it was like the Dub writers didn't understand the character arcs for Yami or Mai in [[AudienceAlienatingEra season four]]. Similar to the Yami Yugi season 4 issue however, this was a consequence of [[DubInducedPlotHole 4Kids' dub-based changes in story and characterization that excised how Mai's actions were a result of her ending up traumatized by what Marik had done to her in the previous season and not dealing with it well]]. A compounding error was the dub's decision to excise and downplay ALL of the antagonist's root trauma's for that season due to them being rooted in Real-world issues that were "too mature for a kids show".
** Happens to Kaiba throughout the series to a lesser extent both canonically and once more due to dub-based exaggerations of character, as he continually forgot lessons about teamwork...though that is more caused by the series' original writer continuously railroading Kaiba into the role of antagonist rival to Yami Yugi even past the point where they'd settled their issues.
* ''Anime/YuGiOh5Ds'':
** For quite a few people, the change in Aki's character was too abrupt, most of it within the space of one or two episodes rather than being more evenly spread out. This was not made better by the Dub skipping episodes and playing them out-of-order which resulted in this feeling.
** This happens to Jack and Carly in the second season/Third of Five Storyarcs. [[TheRival Jack]] [[IgnoredEpiphany forgets everything he learned in the Dark Signer arc]] and becomes more of a ButtMonkey, [[TookALevelInBadass Carly]] is demoted from Jack's LoveInterest to a comic-relief character with little more importance than the rest of his fangirls, etc.
* ''Anime/YugiohVRAINS'': GO Onizuka goes from being Playmaker's hot-blooded, prideful, but good-natured rival who loves to entertain the crowds in the first season to the second making him a power-hungry jerkass who's single-mindedly obsessed with gaining strength and avenging his losses at Playmaker's hands. Explicable due to Vrains not having a consistent writing staff.
* In ''Franchise/TransformersGeneration1'', Cyclonus and Scourge were a pair of dangerous, cunning, devious warriors. In ''Anime/TransformersHeadmasters'', they suddenly became a pair of bumbling idiots who kept getting in Sixshot's way, and wondered why Soundblaster lost all respect for them. They were quietly dropped from the show soon after.
** Rodimus Prime after the movie also suffered derailment, turning from 'plucky youth' into 'useless jerk' over the third and fourth seasons.
* ''Anime/MyOtome'': Nina Wang was introduced and developed as a somewhat FriendlyRival to Arika and a more-than-competent fighter, celebrated as one of the top students at Garderobe Academy. Following the mid-series WhamEpisode, that rivalry collapsed as she underwent a FaceHeelTurn and became a puppet of the BigBad desperate to prove her loyalty to/love for her adoptive father Sergey at the expense of everything else.
* This occurred in ''LightNovel/{{Tytania}}'', and it happened to, of all people, Estrades- the man turns from a calm, devious schemer who was perfectly fine being ordered about by his brother Ajman to a wild, rabid, hateful person who despised his sibling with every fiber of his being. To top it off, his derailment is combined with a severe case of a mixture of the IdiotBall and TooDumbToLive when [[spoiler: he offs himself by shooting himself after tumbling down a flight of stairs.]]
* Dumas from ''Anime/{{Kiba}}'' starts off as the strong, quiet champion of Tempura/Templer, then [[spoiler: makes a shocking FaceHeelTurn and would have lead Jimoto's invaders to overtake Tempura had not Zed's Spirit gone on a rampage and stopped them.]] The really interesting part was that Duma's reasons for this were pretty reasonable: because of his family history, he basically wanted to shape his own destiny. However, after Zed’s Spirit rejected him, which took a toll on his sanity, [[spoiler: he became a regular psychotic baddie whose sole purpose in life was betraying Tempura in every way possible and becoming royalty.]]

* Franchise/{{Gundam}}
** ''[[Anime/MobileSuitZetaGundam Zeta Gundam]]'': Reccoa went from being a fairly capable, trusted member of AEUG with generally straight morals to [[spoiler: a TITANS officer]] who [[spoiler: willingly ''gassed'' an entire colony]]. Admittedly she tried to [[spoiler: delay it in the hopes that the AEUG would stop it]] but she [[spoiler: never attempted to stop it herself]]. This after she [[spoiler: used the evidence of the TITANS gassing a colony]] to convince [[spoiler: Emma to switch sides]] at the start of the series. It's idiotic enough that fans [[{{Fanon}} prefer to believe]] that [[spoiler: Paptimus has some kind of hypnotic Newtype powers that he used on her]].
** ''[[Anime/MobileSuitVictoryGundam Victory Gundam]]'': Due to a combination of ExecutiveMeddling and CreatorBreakdown, Katejina Loos goes from an AntiVillain who had several PetTheDog moments in the first half of the series to a hate-filled, AxCrazy psychopath who crosses the MoralEventHorizon many times over in the second half, with little rhyme or reason behind the change. WordOfGod is that deeper explanations behind her [[JumpingOffTheSlipperySlope descent into evil and madness]] were supposed to be there and paint her as more of a TragicVillain, explanations that are in other media such as the novelization and video games, but in the anime itself it just comes off as a jarring change for the sake of making things DarkerAndEdgier.
** ''[[Anime/MobileSuitGundamAGE Gundam AGE]]'' gives us Zeheart Galette. For most of the show he's a NobleDemon who makes a point of remembering his fallen comrades and subordinates and fights for every Vagan to return to the "Eden" that is Earth. After [[spoiler:Ezelcant reveals his true, SocialDarwinist agenda--the one that had him killing his own citizens--Zeheart devotes himself to it after about thirty seconds of hesitation. By the end, he's willing to throw away the lives of his most loyal aides for the sake of a diversion and wipe out multiple {{Mook}}s into the bargain]]. The OVA ''Memories of Eden'' [[AuthorsSavingThrow explained this]] when he admits [[spoiler:he objected to Ezelcant's true plan, but went through with it since [[SunkCostFallacy those who died under his command would have done so for nothing otherwise]]. It's implied his failure to reconcile these two mindsets led to his subsequent VillainousBreakdown]].

* A case can be made for more than a few of the characters of ''Anime/CodeGeass'', but none more so than [[TheEveryman Ohgi]], initially the voice of reason of the rank-and-file Black Knights who understood the burden of leadership that rested upon Zero, he [[LoveMakesYouDumb lost the plot once he fell for Villetta]] and made many questionable decisions, with ultimately disastrous results. The CompilationMovie series [[AuthorsSavingThrow most likely tried to give him some]] CharacterRerailment by actually attempting to be more reasonable with said decisions, [[InSpiteOfANail which simply didn't affect how everything still went down]].
* Siesta from ''LightNovel/TheFamiliarOfZero'' is a gentle and sweet {{meido}} in the first season, but in the next two she borders on BeAWhoreToGetYourMan, with no logic or explanation.
* [[LightNovel/ACertainMagicalIndex Kuroko]] [[Manga/ACertainScientificRailgun Shirai]] [[ZigZaggedTrope zig zags]] this. In regular plots (Both for ''Index'' and ''Railgun''), she's shown as a competent member of Judgment and a ReasonableAuthorityFigure that just happens to have a crush on a girl, which is PlayedForLaughs but is hardly the only thing she does. In [[{{filler}} anime-only stories]], she suffers from full-blown CharacterExaggeration, becoming a full-blown PsychoLesbian who's willing to resort to drugs to get Mikoto (which she thankfully fails at).
** And yet the second mode [[MisaimedFandom is much more popular]]. While disturbing, it arguably makes Kuroko a [[Administrivia/TropesAreTools more interesting character]]. Note that the more [[RuleOfFunny exaggerated jokes]] in the series are not treated quite literally, as while Mikoto will sometimes reduce Kuroko to [[ComedicSociopathy a smoking crisp]] in revenge for her antics, she hesitated to use her power against a suit a power armor she assumed had a person in it, and her electricity had realistic and debilitating effects in her fight against Frenda.
* ''LightNovel/BakaAndTestSummonTheBeasts'' did this to poor Mizuki Himeji. In the first season she was a nice, sweet girl, with one scene hinting at {{yandere}}-ish HiddenDepths but mostly as an one-off gag and nothing serious. Come the OVA and second season, she's basically reduced to that half the time. Thankfully, the last episodes seems to bring her back to rails.
* Kanade and Usami are both getting hit by this on ''LightNovel/MayoChiki''. Kanade is going from a sexually dominant, but playful and overall nice girl to a {{jerkass}} {{troll}} that has no problem on causing property damage and intimidating others with her BattleButler. Usami went from a nice {{tsundere}} to a generic angry tsundere, overlapping with CharacterExaggeration. Kanade eventually gets better, Usami.... is DemotedToExtra so nobody knows.
** However, both pale compared to UnluckyEverydude Kinjirou in the GeckoEnding. To summarize, the entire show is about him having gynophobia (fear of women) and the other girls trying to help him with that. Unlike some harem mains, he's not a pervert nor anything like that, and in fact the girls are worse than him. But in the GeckoEnding, he suddenly becomes a ''very generic'' pervert that nosebleeds when he sees Usami's panties and can't stop thinking of having sex with [[OfficialCouple Subaru]]. Which is the exact opposite of how he normally is. He also gets CharlesAtlasSuperpower out of freaking nowhere.
* In ''Anime/PuellaMagiMadokaMagica'', Kyosuke Kamijou (Sayaka's ChildhoodFriend love interest, who seems to think his relationship with her as strictly platonic) and Hitomi Shizuki (one of Sayaka's friends and TheRival for Kyosuke's heart) inadvertently [[spoiler:send Sayaka on her StartOfDarkness]]. However, their actions in the anime [[HumansAreFlawed are somewhat understandable]] and they try to give Sayaka a chance (e.g. Hitomi tells Sayaka to face her feelings and gives her a day to confess to Kamijou). Both Hitomi and Kyosuke were unaware of all the problems that Sayaka had [[spoiler: such as Sayaka finding out that her soul got ripped out of her body and put into a SoulJar because no one tells Hitomi and Kyusuke anything. After Sayaka's death, it is revealed that Hitomi fell into depression and thinks [[ItsAllMyFault it's all her fault]] while Kamijou also seems to miss Sayaka.]] Unfortunately, these shades of gray are all dumped in the PSP game. In a certain route in the game [[spoiler:[[RonTheDeathEater Hitomi becomes a full-on]] [[AlphaBitch Alpha]] BitchInSheepsClothing, while when Sayaka starts decomposing due to her distance from her Soul Gem Kyosuke calls her "a disgusting (understandable) ''monster'' (not so much)", then [[KickTheDog twists the knife further]] by adding "Shizuki is the only one I need!"]] Ouch. However, the outcome of this game does depend on how you play it, so there are some scenarios where Hitomi and Kyosuke don't get character derailment (including a route where Sayaka ultimately gets happiness with Kyosuke).
%% Do not add Homura Akemi from Rebellion without approval or [[https://tvtropes.org/pmwiki/remarks.php?trope=CharacterDerailment.AnimeAndManga#109078 discussing here]].
* ''Manga/{{Naruto}}'':
** During his first appearance Obito Uchiha was a guy who strongly believed in ThePowerOfFriendship and could be the potential WhiteSheep of the Uchiha, but after TheReveal he turns out to be Tobi, a ruthless villain who wants to throw the world into despair and isn't afraid to threaten and harm newborns. And all because Rin died, which was perceived by some as a poorly-executed FreudianExcuse.
** Sasuke Uchiha after his FaceHeelTurn showed himself as completely selfish person, who did not care about anything but his revenge (at first Itachi, then Konoha) but after speaking with a resurrected Itachi and a previous Hokage, he suddenly becomes a WellIntentionedExtremist wishing to organize a revolution in order to become a Hokage similar to how Itachi lived. And all this only in order to eventually lose a fight against Naruto and then change his mind afterwards.
** Before Madara's resurrection, Black Zetsu is shown to be a loyal servant of Akatsuki and Tobi spawned from from Madara's will who was willing to do whatever the latter needed to do with absolutely no indication of a scheme or treachery. In fact, when he forced Tobi to resurrect Madara, he actually apologize for being forced to do it. But when Madara is revived, Black Zetsu all of a sudden is revealed to be just as callous as Madara who berates Obito for not following Madara's plans. To add the derailment even further, at the turning point of the story, [[DroppedABridgeOnHim he backstabs Madara]] [[AssPull revealing that all along he is in fact, a will of Kaguya, despite previously having virtually no indication that he worked for Kaguya in the first place]].
* The [[DownerEnding ending]] for ''Manga/AttackOnTitan'' was controversial due to Eren's characterization taking a full 180. Beforehand, he was a sympathetic WoobieDestroyerOfWorlds who was willing to do whatever it takes for the sake of freedom for his people and avenging his mother's death. However in the final chapters it's revealed that through the TimeyWimeyBall he was ''directly responsible'' for his mother's death BecauseDestinySaysSo, erasing all his motivations and convictions, making him into a {{hypocrite}} and the TheReasonYouSuckSpeech he gave Reiner completely meaningless.

* In ''Manga/{{Bleach}}'' Uryu seemingly has forgotten about how Mayuri tortured his grandfather to death. Instead of displaying open hatred for Mayuri when they meet up again, he only seems mildly annoyed with Mayuri, and his reaction is PlayedForLaughs. The show seems to be glossing over the first time they met and what Mayuri did to his grandfather and his entire clan. Sure, Uryu in the second meeting wasn't in a position to ''do anything'' about his hatred of Mayuri, being too badly injured to even stand up, but if anything that should make him him even ''angrier''.
** Yukio and Giriko from the Fullbring arc. They are each calm and quiet normally, but after receiving Ichigo's power, it went to their heads, causing them to become loud and boastful, Yukio declaring himself a [[AGodAmI god.]] Yukio, at least, seemed to return to normal after having the extra power taken away, so it may be a case of DrunkOnTheDarkSide.
** As WebVideo/YRulerOfTime points out, Orihime undergoes by this for the Hueco Mundo arc. She started the series having a lot of CharacterDevelopment, by learning how her powers work, being ThePollyanna in front of her bullies or enemies and being the optimistic BunnyEarsLawyer. Once the Arrancar Arc started, Orihime was demoted to LivingMacGuffin DamselInDistress, who could only wait to be rescued and cry for Ichigo to save her.
* In the ''Manga/KOn'' [[TheMovie movie]], Azusa becomes quite upset about the idea that Yui might have romantic feelings for her. Quite a few fans thought this was odd. Azusa might get exasperated by Yui's antics at times in the manga, but it was clear she wasn't against Yui's affection for her ''in principle'', and in the end, even got very close to confessing her feelings to Yui ''herself''. From the other perspective, it can also be seen as derailing Yui from a simple CuddleBug to someone who uncomfortably won't take no for an answer.

* ''Franchise/DragonBall'':
** Goku's wife Chi-Chi is introduced in the [[Manga/DragonBall original series]] as a strong, capable fighter in her own right, even convincing Goku to agree to marry her as a result of the fierce fight she puts up in a world-class martial arts tournament. Come ''Anime/DragonBallZ'', and she's basically abandoned all about her combat skills to become a parody of an EducationMama with severely SkewedPriorities & InsaneTrollLogic to boot. While it doesn't excuse her SkewedPriorities, InsaneTrollLogic, and some of her other undesirable traits, this may be somewhat justified. This is because dealing with your family members being constantly put in danger will drive the most rational parent insane. It doesn't help that Goku was even ''killed'' and Gohan has been kidnapped and brutally injured. With Super, however, she has no excuse. The Buu Arc fixes this somewhat.
** ''Anime/DragonBallGT'' did this to Pan. In ''Z,'' she's introduced as a bubbly, headstrong 4-year-old girl. Come GT, and she's introduced as a MouthyKid and a BrattyHalfPint towards Trunks and her own grandpa, althought the time difference is long enough for her personality to have changed.
** ''Anime/DragonBallSuper'' unfortunately reverts Chi-Chi back to her old ways. In ''DBZ'' she seemed to mellow out after Goku died fighting Cell, even training their second son Goten in martial arts personally. In ''Super'', not only does she start displaying the same EducationMama attitude towards Goten, but in one episode she is once again, too protective of her family members. She even goes as far as to kidnap her granddaughter away from Gohan because he and Mr. Satan discussed the possibility of her being a martial artist when she grows up.

* The last few episodes of ''Anime/LeChevalierDEon'' do this with Robin. He goes from being friends with and saving D'eon's life to indifferent and willing to fight him, while instead teaming up with the main villain for the series. They tried to write in reason for it... but just didn't sell it very well.
* One of the big problems that people have pertaining to the last couple volumes of ''Manga/NegimaMagisterNegiMagi'' has to do with one of its final storylines, the Sports Festival arc. The arc, which involves [[spoiler: cheerlearder Misa convincing most of Class 3-A that Negi is a philanderer (despite the fact that he's just a kid with no real concept of romance and that most of the escapades involving that were forced upon him by his students) and that they should use the final event of the school's Sports Festival to teach him a lesson about being a womanizer]], took most of the character development that happened in the past 343 chapters (and some elements from early in ''the first chapter of the arc'') and basically threw it out the window for the sake of story that basically incorporates the ComedicSociopathy aspect of Ken Akamatsu's previous work, ''Manga/LoveHina''. Even those students that should know better, like Setsuna and Kaede, windd up acting out of character in this arc and side with the rest of the class in terms of causing trouble for their teacher. It also doesn't help that the climax of the story involves [[spoiler: the students basically raping Negi by sticking Chizuru's spring onion Pactio item up his butt, with Nodoka and Yue finally having enough of this crap to come to his aide]].

** Mai in Season 4, when she [[FaceHeelTurn joins the bad guys briefly]] and all her characterisation appears lost. Creator/LittleKuriboh of [[WebVideo/YuGiOhTheAbridgedSeries Yu-gi-oh! Abridged]] even lampshaded at one point that it was like the Dub writers didn't understand the character arcs for Yami or Mai in [[DorkAge season four]]. Similar to the Yami Yugi season 4 issue however, this was a consequence of [[DubInducedPlotHole 4Kids' dub-based changes in story and characterization that excised how Mai's actions were a result of her ending up traumatized by what Marik had done to her in the previous season and not dealing with it well]]. A compounding error was the dub's decision to excise and downplay ALL of the antagonist's root trauma's for that season due to them being rooted in Real-world issues that were "too mature for a kids show".

*** Unfortunately, this is a result of [[RealitySubtext real-world events screwing the show over]] which resulted in the show's mid-production direction-change that plagued the entire third story arc. A cult [[RealLifeWritesThePlot conspicuously similar to the psychic cult in the]] series performed a terrorist attack during the period 5D's was on the air, forcing most of the storyline the show had planned to run with entirely thrown out, leading to a scramble for a new direction that wasn't found until the tie-in crossover film and fourth arc of the series started. Worse, Carly's voice actress was ''a member'' of said cult, making the producers forcibly demote the role and their romance until they had sufficient cause to fire her and recast the role...around episode 140 when the show was wrapping up.
* ''Anime/YugiohVRAINS'': GO Onizuka goes from being Playmaker's hot-blooded, prideful, but good-natured rival who loves to entertain the crowds in the first season to the second making him a power-hungry jerkass who's single-mindedly obsessed with gaining strength and avenging his losses at Playmaker's hands. Explicable due to Vrains not having a consistent writing staff.

** Ash's Charmander, upon evolution into Charmeleon, goes from arguably the nicest of Ash's Kanto starters to volatile and uncontrollable. Upon evolution into Charizard, it becomes a complete JerkAss that rarely even tolerates Ash until halfway through the Orange Islands arc when Ash saves its life (again). While Charizard's behavior was intended to teach Ash some humility, it still comes completely out of nowhere and is treated entirely as Ash's fault, [[InformedWrongness even though he]] ''[[InformedWrongness had]]'' [[InformedWrongness tried controlling it before and Charizard actively refused to cooperate]].
** Cassidy and Butch while initially popular characters being serious foils to Jessie and James fell into this after a severe case of BadassDecay and Flanderization in 'Anime/PokemonChronicles''. In this series of side stories, the two strong schemers became copies of Jessie and James without any of the HiddenDepths that made the two popular, to begin with. "Training Daze" in particular hurt their image as being a FullEpisodeFlashback it retroactively made them ALWAYS inferior to Jessie and James which was the exact opposite of their original intent. This derailment would carry over to the Main Series and might be why the duo made no appearances from Gens V-VII. When the duo finally returned in Journeys it was revealed that they had quit Team Rocket and began an honest living which can either be seen as rerailment for regaining competence or further derailment for giving up their evil ambitions.
** The ''Best Wishes'' series is infamous for its heavy derailment of Ash himself. After the previous four regions had developed him into a powerful, strategic battler nearly on par with top-level Trainers, Unova rebooted him into a complete rookie who had forgotten even the barest basics. He regresses back to Kanto-era levels of relying more on luck than skill, and it's treated as a complete shock when Ash actually pulls off anything genuinely clever.
*** Possibly the most egregious example is in his Gym battle against Elesa. He spends hours prior to the battle trying to prepare a strategy for her, only to come up with something completely idiotic: benching his ''entire team'' in favor of his inexperienced Palpitoad, expecting to sweep her clean with just one Pokemon. In the end, he chooses to '''disregard strategy entirely''' and just rely purely on Pikachu, [[BrokenAesop not considering that the strategy itself might have just been terrible]].
*** There is a smaller group that suggests Ash's biggest regression was not Unova but rather Alola. As while he was more competent than he was in Best Wishes [[spoiler: with Ash FINALLY winning a Pokemon League]] it's been observed his MATURITY seemed to be at a low not seen since Kanto. In Sun & Moon Ash spends very little time training, often being treated as a Butt-Monkey getting into trouble, and many instances of irresponsibility like trying to cheat on an exam. It's also been argued the idea that Ash would ever want to go to School rather than travel is completely antithetical to his character (which is supported by the alternate universe "I Choose You" which suggests Ash's greatest fear is having to go to school).

** In mid-Sinnoh, Ambipom is literally PutOnABus for incredibly contrived reasons that make no sense given the Pokemon's previously established character. From the beginning Aipom/Ambipom was shown to love Contests, which eventually led to her getting traded to Dawn, the Contest Coordinator of the group. [=DP124=] has the characters participating in [[MundaneUtility Pokemon Ping Pong,]] and Ambipom suddenly decides to leave her trainer and the Contests she loved so much to go off with a complete stranger and train for an activity she didn't even know existed before the previous episode.
** Ash's Pikachu started out as bratty and self-centered but over time received character development to become a natural leader, who acted as a mediator to other Pokemon and had full loyalty to Ash. A common plot of Pikachu shorts (and the occasional filler episode) would be Pikachu being left in charge while the humans were away and struggling to control the chaos caused by the other Pokemon. Come Sun & Moon and Pikachu began to regress to how he was in Kanto becoming more selfish, rebellious, and mischievous, often ignoring Ash's orders and even attacking him for fun on occasion. If anything Pikachu became the most mischief-prone of Ash's Alola team and acted more like a child than a leader. This regression sadly progressed to Journies and became even worse. In episode 30 Pikachu was willing to run away from Ash all because he was spending time with Riolu. A Pokemon is a baby which by nature requires extra attention. Pikachu understood this with Phanpy, Larvitar, Scraggy, and Noibat. Yet, suddenly Pikachu believes Ash no longer loves him. To add salt to the wound when Ash apologizes Pikachu accepts the apology... only after electrocuting Ash.

* One of the big problems that people have pertaining to the last couple volumes of ''Manga/NegimaMagisterNegiMagi'' has to do with one of its final storylines, the Sports Festival arc. The arc, which involves [[spoiler: cheerlearder Misa convincing most of Class 3-A that Negi is a philanderer (despite the fact that he's just a kid with no real concept of romance and that most of the escapades involving that were forced upon him by his students) and that they should use the final event of the school's Sports Festival to teach him a lesson about being a womanizer]], took most of the character development that happened in the past 343 chapters (and some elements from early in ''the first chapter of the arc'') and basically threw it out the window for the sake of story that basically incorporates the ComedicSociopathy aspect of Ken Akamatsu's previous work, ''Manga/LoveHina''. Even those students that should know better, like Setsuna and Kaede, windd up acting out of character in this arc and side with the rest of the class in terms of causing trouble for their teacher.

*** There is a smaller group that suggests Ash's biggest regression was not Unova but rather Alola. As while he was more competent than he was in Best Wishes [[spoiler: with Ash FINALLY winning a Pokemon League]] it's been observed his MATURITY seemed to be at a low not seen since Kanto. In Sun & Moon Ash spends very little time training, often being treated as a Butt-Monkey getting into trouble, and many instances of irresponsibility like trying to cheat on an exam. It's also been argued the idea that Ash would ever want to go to School rather than travel is completely antithetical to his character (which is supported by the alternate universe "I Choose You" which suggests Ash's greatest fear is having to go to school instead of travel).

*** There is a smaller group that suggests Ash's biggest regression was not Unova but rather Alola. As while he was more competent than he was in Best Wishes [[spoiler: with Ash FINALLY winning a Pokemon League]] it's been observed his MATURITY seemed to be at a low not seen since Kanto. In Sun & Moon Ash spends very little time training, often being treated as a Butt-Monkey getting into trouble, and many instances of irresponsibility like trying to cheat on an exam. It's also been argued the idea that Ash would ever want to go to School rather than travel is completely antithetical to his character (which is supported by the alternate universe "I Choose You" where Ash has a nightmare about going to school).

*** There is a smaller group that suggests Ash's biggest regression was not Unova but rather Alola. As while he was more comptent than he was in Best Wishes [[spoiler: with Ash FINALLY win a Pokemon Leauge]] it's been observed his MATURITY seemed to be at a low not seen since Kanto with Ash spending very little time training, often being treated as a Butt-Monkey and even trying to cheat on an exam. It's also been argued the idea that Ash would want to ever go to School rather than travel is completely antithetical to his character (which is supported by the alternate universe "I Choose You" where Ash has a nightmare about going to school).

** Cassidy and Butch while initially popular characters being serious foils to Jessie and James fell into this after a severe case of BadassDecay and Flanderization in 'Anime/PokemonChronicles''. In this series of side stories the two strong schemers became copies of Jessie and James without any of the HiddenDepths that made the two popular, to begin with. "Training Daze" in particular hurt their image as being a FullEpisodeFlashback it retroactively made them ALWAYS inferior to Jessie and James which was the exact opposite of their original intent. This derailment would carry over to the Main Series and might be why the duo made no appearances from Gens V-VII.

* The [[DownerEnding ending]] for ''Manga/AttackOnTitan'' was controversial due to Eren's characterization taking a full 180. Beforehand, he was a sympathetic WoobieDestroyerOfWorlds who was willing to do whatever it takes for the sake of freedom for his people and avenging his mother's death. However in the final chapters it's revealed that through the TimeyWimeyBall he was ''directly responsible'' for his mother's death BecauseDestinySaysSo, erasing all his motivations and convictions, making him into a {{hypocrite}} and the TheReasonYouSuckSpeech he gave Reiner completely meaningless. In the eyes of many longtime fans it was essentially a retelling of the end of ''Series/GameOfThrones''.

** During his first appearance Obito Uchiha was a guy who strongly believed in ThePowerOfFriendship and could be the potential WhiteSheep of the Uchiha, but after TheReveal he turns out to be Tobi, a ruthless villain who wants to throw the world into despair and isn't afraid to threaten and harm newborns. And all because Rin died that perceived by some as poorly executed a FreudianExcuse.

** Before Madara's resurrection, Black Zetsu is shown to be a loyal servant of Akatsuki and Tobi spawned from from Madara's will who was willing to do whatever the latter needed to do with absolutely no indication of a scheme or treachery. In fact, when he forced Tobi to resurrect Madara, he actually apologize for being forced to do it. But when Madara is revived, Black Zetsu all of a sudden is revealed to be just as callous as Madara who berates Obito for not following Madara's plans. To add the derailment even further, at the turning point of the story, he backstabs Madara [[AssPull revealing that all along he is in fact, a will of Kaguya, despite previously having virtually no indication that he worked for Kaguya in the first place]].

* For the first three seasons of ''Anime/CardfightVanguardG'', Chrono is very empathetic and responsible, and always trying to take care of others, even at his most standoffish. He values honesty and openness greatly - he routinely shares everything he knows about whatever plot is going on with his friends and teammates, and hates being kept in the dark by others himself. Come season NEXT, he's suddenly extremely pushy and oblivious to other's feelings, keeps plot-related secrets from everyone including his own team, and prioritizes winning a card game tournament over actually saving someone from a forced possession by the season's BigBad.

* Ash's Pikachu started out as bratty and self-centered but over time received character development to become a natural leader, who acted as a mediator to other Pokemon and had full loyalty to Ash. A common plot of Pikachu shorts (and the occasional filler episode) would be Pikachu being left in charge while the humans were away and struggling to control the chaos caused by the other Pokemon. Come Sun & Moon and Pikachu began to regress to how he was in Kanto becoming more selfish, rebellious, and mischievous, often ignoring Ash's orders and even attacking him for fun on occasion. If anything Pikachu became the most mischief-prone of Ash's Alola team and acted more like a child than a leader. This regression sadly progressed to Journies and became even worse. In episode 30 Pikachu was willing to run away from Ash all because he was spending time with Riolu. A Pokemon is a baby which by nature requires extra attention. Pikachu understood this with Phanpy, Larvitar, Scraggy, and Noibat. Yet, suddenly Pikachu believes Ash no longer loves him. To add salt to the wound when Ash apologizes Pikachu accepts the apology... only after electrocuting Ash.

* Ash's Pikachu started out as bratty and self centered but overtime recived character development to become a natural leader, who acted as a mediator to other Pokemon and had full loyalty to Ash. Come Sun & Moon and Pikachu began to regress to how he was in Kanto becoming more selfish, rebellious and mischevious, often ignoring Ash's orders and even attacking him for fun on occasion. This regression sadly progessed to Journies an became even worse there as Pikachu was willing to run away from Ash all because he was spending time with Riolu. A Pokemon who is a baby which by nature require extra attention. Pikachu understood this with Phanpy, Larvitar, Noibat, and Scraggy, yet suddenly he belives Ash no longer loves him. To add salt to the wound when Ash apologizes Pikachu accepts the apology... only after electrocuting Ash.

* ''Anime/{{Pokemon}}'':
** Ash's Charmander, upon evolution into Charmeleon, went from arguably the nicest of Ash's Kanto starters to volatile and uncontrollable. Upon evolution into Charizard, it went even further to a complete JerkAss that would rarely even tolerate Ash until halfway through the Orange Islands arc when Ash saved its life (again). While Charizard's behavior was intended to teach Ash some humility, it still comes completely out of nowhere and treated entirely as Ash's fault, [[InformedWrongness even though he]] ''[[InformedWrongness had]]'' [[InformedWrongness tried controlling it before and Charizard actively refused to cooperate]].

** In mid-Sinnoh, Ambipom was literally PutOnABus, for incredibly contrived reasons that made no sense given the Pokemon's previously established character. From the beginning Aipom/Ambipom was shown to love Contests, which eventually led to her getting traded to Dawn, the Contest Coordinator of the group. [=DP124=] has the characters participating in [[MundaneUtility Pokemon Ping Pong,]] and Ambipom suddenly decides to leave her trainer and the Contests she loved so much to go off with a complete stranger and train for an activity she didn't even know existed before the previous episode.

** Mai in Season 4, when she [[FaceHeelTurn joins the bad guys briefly]] and all her characterisation appears lost. Creator/LittleKuriboh of [[WebVideo/YuGiOhTheAbridgedSeries Yu-gi-oh! Abridged]] even lampshaded at one point that it was like the Dub writers didn't understand the character arcs for Yami or Mai in [[DorkAge season four]]. Similar to the Yami Yugi season 4 issue however, this was a consequence of 4kids' dub-based changes in sotry and characterization that excised how Mai's actions were a result of her ending up traumatized by what Marik in the previous season had done to her and not dealing with it well. A compounding error was the dub's decision to excise and downplay ALL of the antagonist's root trauma's for that season due to them being rooted in Real-world issues that were "too mature for a kids show".
** Happens to Kaiba throughout the series to a lesser extent both canonically and once more due to dub-based exhaggerations of character, as he continually forgot lessons about teamwork...though that is more caused by the series' original writer continuously railroading Kaiba into the role of antagonist rival to Yami Yugi even past the point where they'd settled their issues.

*** Unfortunately This is a result of Real-world events screwing the show over which resulted in the show's mid-production direction-change that plagued the entire third storyarc. A cult conspicuously similar to the psychic cult in the series performed a terrorist attack during the period 5D's was on the air, forcing most of the storyline the show had planned to run with be entirely thrown out, leading to a scramble for a new direction that wasn't found until the Tie-in crossover film and Fourth arc of the series started. Worse, Carly's Voice actress was A MEMBER of said Cult, making the producers forcibly demote the role and their romance until they had sufficient cause to fire her and recast the role...around episode 140 when the show was wrapping up.

* Nina Wang got hit with this ''hard'' after [[WhamEpisode Episode 16]] of ''Anime/MyOtome''. Before, she was a somewhat friendly [[TheRival rival]] to Arika and a more-than-competent fighter on track to become one of the greatest Otome ever. Afterward, she [[spoiler:underwent a FaceHeelTurn and killed tens of thousands of people to prove her loyalty to/love for her "father"]], and her rivalry was thrown on the back burner for all but one or two episodes during that period, and her position was snapped up by Tomoe for [[UnknownRival reasons unknown to Arika]].

** This befalls the Team Rocket Trio in ''Best Wishes'' as well, effectively meaning that all returning characters in the series (except maybe [[SeriesMascot Pikachu]]) are derailed in some form. The trio is usually portrayed as [[IneffectualSympatheticVillain comical, bumbling villains]], each of them having a developed personality (Jessie is [[{{Tsundere}} bossy and grumpy but occasionally sweet]], James is [[MinionWithAnFInEvil kind and caring]], and Meowth is [[DeadpanSnarker sneaky and sarcastic]]) as well as surprisingly deep backstories. They're also often hinted to [[AntiVillain not really be entirely bad people]]. In an attempt to make them competent villains, this series throws all of this out of the airlock. The characters [[DemotedToExtra barely appear and don't get much focus when they do]], and their personalities are extremely diluted to the point of almost being interchangeable, usually being depicted as merely doing villainy and lacking all of their character quirks from previous series. The implication is that they're taking their jobs more "seriously" since they've been promoted, but the personality change is radical and extremely abrupt, making it very jarring. This decision proved controversial and has since been largely reverted in later series.

** Before Madara's resurrection, Black Zetsu is shown to be a loyal servant of Akatsuki and Tobi spawned from from Madara's will who was willing to do whatever the latter needed to do with absolutely no indication of a scheme or treachery. In fact, when he forced Tobi to resurrect Madara, he actually apologize for being forced to do it. But when Madara is revived, Black Zetsu all of a sudden is revealed to be just as callous as Madara who berates Obito for not following Madara's plans. To add the derailment even further, [[ShockingSwerve at the turning point of the story,]] he backstabs Madara revealing that all along he is in fact, a will of Kaguya, despite previously having virtually no indication that he worked for Kaguya in the first place.

* Nina Wang got hit with this ''hard'' after [[WhamEpisode Episode 16]] of ''Anime/MaiOtome''. Before, she was a somewhat friendly [[TheRival rival]] to Arika and a more-than-competent fighter on track to become one of the greatest Otome ever. Afterward, she [[spoiler:underwent a FaceHeelTurn and killed tens of thousands of people to prove her loyalty to/love for her "father"]], and her rivalry was thrown on the back burner for all but one or two episodes during that period, and her position was snapped up by Tomoe for [[UnknownRival reasons unknown to Arika]].

** Ash's Charmander, upon evolution into Charmeleon, went from nice compared to Ash's other Kanto starters to volatile and uncontrollable. Upon evolution into Charizard, it went even further to a borderline jerk that actually seemed to dislike Ash until halfway through the Orange Islands arc because Ash spent a lot of time and effort to keep it alive. It was probably supposed to be similar to traded Pokemon above a certain level refusing to obey their trainers without a certain badge in the games, but he still remained disobedient even after Ash had gotten all eight badges. The show can't seem to decide whether or not evolving changes who you are (Charmander's personality changes, Pikachu and Bulbasaur directly refuse to evolve) or if it changes your form but nothing else (most other evolutions including a Magikarp that retained its sweet personality for the Joy that looked after it).
** Brock was the voice of reason with occasional attraction toward girls in Kanto. When he got back from his [[PutOnABus bus trip]] during the Orange Islands FillerArc, he became an obsessive love freak every time he sees a beautiful woman. And his voice of reason status has apparently been reduced to just explaining to his comrades (and the audience) [[CombatCommentator every single move]] that gets made during a battle. The writers caught on by the end of the Sinnoh arc and gave him a [[PutOnABus mercy bus ride.]]
** Considering that Ash has battled various opponents in the past with impressive feats, you'd think he'd be able to beat a rookie like Trip without getting his ass handed to him. Other than their first battle where Pikachu was weakened by Zekrom’s lightning, there is no excuse whatsoever that Ash should lose to a beginner trainer, other than only using Pokémon he caught in Unova.
** In mid-Sinnoh, Ambipom was literally PutOnABus, for incredibly contrived reasons that made no sense given the Pokemon's previously established character. From the beginning Aipom/Ambipom was shown to love Contests, which eventually led to her getting traded to Dawn, the Contest Coordinator of the group. DP 124 has the characters participating in [[MundaneUtility Pokemon Ping Pong,]] and Ambipom suddenly decides to leave her trainer and the Contests she loved so much to go off with a complete stranger and train for an activity she didn't even know existed before the previous episode.