History Main / SplitPersonalitySwitchTrigger

* ''Manga/DragonBall'': Launch/[[SpellMyNameWithAnS Lunch]] turns back and forth from a blue-haired kind-hearted Ditz, and a blonde-haired and violent "Kushami" form, whenever she sneezes.

* Yamamoto Jun from ''Manga/SpecialA'' turns from a relatively shy guy to ThrCasanova whenever he is kissed by a girl. Later on, it seems to be when a certain girl just looks at him.

* Yamamoto Jun from ''Manga/SpecialA'' turns from a relatively shy guy to a {{Casanova}} whenever he is kissed by a girl. Later on, it seems to be when a certain girl just looks at him.

* Suzuho in ''LightNovel/MagiciansAcademy'' is usually quiet and meek, communicating only through [[TalkingWithSigns sketchbook messages]]. When she removes her ribbon, her other side comes out, which is the exact opposite in personality. Violent, talkative, and, for some reason, blue-haired.

* Using hypnosis, the protagonists of ''Literature/CaptainUnderpants'' cause their mean teacher Mr. Krupp to change into the titular superhero when someone snaps their fingers in his presence, leading to {{hilarity|Ensues}} when they realize this means other people can cause the switch by pure accident, and in fact, the man himself inadvertently does this at one point when he snaps his fingers to get their attention. However, Captain Underpants can then be switched back to Krupp by being splashed with water. This, too, is by design, as Krupp will be very furious and humiliated when he finds he's soaking wet and half-naked for no reason he can think of.

* ''Manga/GTOTheEarlyYears'': Eikichi spends the whole beach trip in Chapter 110 trying to figure out what this is for Nagisa. As they're leaving, Ryuji realizes it's the sound of a motorcyle engine, when she turns into [[SuperpoweredEvilSide Yasha]] and attacks him after Eikichi revs his bike.

* [[ComicBook/SuicideSquad June Moone]] is an innocent graphic designer who is possessed by an evil sorceress known as the Enchantress. June can actually voluntarily let Enchantress take control by speaking her name; however, the witch has also been known to take over their shared body during moments of intense stress.

* ''VideoGame/GalaxyAngelII'': Kahlua Marjoram turns into her SexierAlterEgo Tequila by ingesting any amount of alcohol (usually provided by Mimolette with a liquor-filled bonbon). Tequila however is able to switch back to Kahlua at will.

[[folder:Visual Novel]]

* ''ComicBook/IncredibleHulk'': Some, but not all, of Bruce Banner's alters can only come out [[NighttimeTransformation at night]]. This includes Joe Fixit and ComicBook/ImmortalHulk. In the latter's own series, it's said to be associated with how much Banner fears and distrusts that particular personality: As they [[SplitPersonalityTeam start cooperating more]], Joe flips to only being able to come out by day, and Immortal Hulk is shown becoming more and more resistant to the daylight...[[note]]''Hulk: ComicBook/SeasonOne'' has Bruce speculating that it's actually the decrease in atmospheric compton scattering that triggers the change, instead of his mind processing the information that it's nighttime. But he isn't sure and thinks that explanation might just be a HandWave.[[/note]] The regular 'Jade Giant' version of the character has the more popular trigger of '[[HulkingOut anger]]'.

* ''Anime/YuGiOh'': Marik's dark alter ego emerges whenever Odion is injured or unconscious.

* ''Franchise/{{Danganronpa}}'': Toko Fukawa switches between her SerialKiller alter ego of Genocide Jack and back when they either sneeze or fall unconscious. By ''[[VideoGame/DanganronpaAnotherEpisodeUltraDespairGirls Ultra Despair Girls]]'', Toko has discovered she can also intentionally switch into Genocide Jack temporarily by zapping herself in the head with a taser; the more power she uses, the longer it lasts. Kids, don't try this at home!

* ''Manga/DragonBall'': Launch/[[SpellMyNameWithAnS Lunch]] turns into her blonde-haired and violent "Kushami" form and back whenever she sneezes.

* ''Franchise/{{Danganronpa}}'': Toko Fukawa switches between her SerialKiller alter of Genocide Jack and back when they either sneeze or fall unconscious. By ''[[VideoGame/DanganronpaAnotherEpisodeUltraDespairGirls Ultra Despair Girls]]'', Toko has discovered she can also intentionally switch into Genocide Jack temporarily by zapping herself in the head with a taser; the more power she uses, the longer it lasts. Kids, don't try this at home!

* ''Anime/YuGiOh'': Marik's dark alter emerges whenever Odion is injured or unconscious.

* ''Manga/ShonanJunaiGumi'': Eikichi spends the whole beach trip in Chapter 110 trying to figure out what this is for Nagisa. As they're leaving, Ryuji realizes it's the sound of a motorcyle engine, when she turns into [[SuperpoweredEvilSide Yasha]] and attacks him after Eikichi revs his bike.

* Jeni Hayes, whose case was made famous in 2019 after she (or rather, six of her alters) testified against her abusive father, had 2500 alternate selves, several of which had triggers. Her first, Symphony, came out whenever Jeni was about to be abused by her father (according to her, "She suffered every minute of Dad's abuse and when he abused me, his daughter Jeni, he was actually abusing Symphony"), but she developed several more as time went on, with triggers such as a particular sight or smell.

A SplitPersonality doesn't always switch at random. Many of them have a specific trigger associated with one or more personalities that cause them to come to the forefront. The large majority of examples use [[YouWouldntLikeMeWhenImAngry anger]] as the trigger, but there are some that are more specific. Examples that are PlayedForDrama might have the trigger be associated with some episode of the characters' DarkAndTroubledPast. This is TruthInTelevision; Most real cases of DID are the result of severe trauma experienced in childhood, and as such, the [[TraumaButton factors associated with such trauma]] will cause the alternate personality to take over and protect the person from being reminded of their past.

* {{Deconstructed|Trope}} with [[ComicBook/TyphoidMaryMarvelComics Mary Walker]] in ''Series/IronFist2017'' Season 2. Mary switches to Walker when she's in danger or stressed, as is typical for most fictional DID depictions, but Walker switches to Mary if she's in the presence of rushing water or flickering lights. Imagine going into a fugue state because someone unknowingly opened up a faucet in front of you and only waking up months later because your alter decided to watch a horror movie.

* In ''Manga/ShokugekiNoSoma'', Ryou Kurokiba switches between his stoic, laid-back regular personality and the rude, hot-blooded personality he has when he's cooking when he puts on his bandanna.

* In the NotSafeForWork anime ''Sprite: Between Two Worlds'', meek and submissive ShrinkingViolet Manami turns into her assertive, self-confident alter-ego Nami whenever she hears the name Nami.
* In the Creator/FUNimation dub of Manga/CrayonShinChan, the normally sweet and shy (but still CovertPervert) Miss Polly turns into a full-on {{dominatrix}} if you remove her glasses.
* In the Crossfire side-stories of ''Manga/{{Hellsing}}'', sweet, pacifistic nun Yumiko Takagi turns into berserker Iscariot swordswoman Yumie Takagi whenever she takes off her glasses. Whether that is also true in the main storyline is uncertain, as Yumie is the only one of her to appear.

A SplitPersonality doesn't switch at random. Many of them have a specific trigger associated with one or more personalities that cause them to come to the forefront. The large majority of examples use [[YouWouldntLikeMeWhenImAngry anger]] as the trigger, but there are some that are more specific. Examples that are PlayedForDrama might have the trigger be associated with some episode of the characters' DarkAndTroubledPast. This is TruthInTelevision; Most real cases of DID are the result of severe trauma experienced in childhood, and as such, the [[TraumaButton factors associated with such trauma]] will cause the alternate personality to take over and protect the person from being reminded of their past.

A SplitPersonality doesn't always switch at random. Many of them have a specific trigger associated with one or more personalities that cause them to come to the forefront. The large majority of examples use [[YouWouldntLikeMeWhenImAngry anger]] as the trigger, but there are some that are more specific. Examples that are PlayedForDrama might have the trigger be associated with some episode of the characters' DarkAndTroubledPast. This is TruthInTelevision; Most real cases of DID are the result of severe trauma experienced in childhood, and as such, the [[TraumaButton factors associated with such trauma]] will cause the alternate personality to take over and protect the person from being reminded of their past.

* ''Franchise/{{Danganronpa}}'': Touko Fukawa switches between her SerialKiller alter Genocider Syo and back when either of them sneezes or falls unconscious. By ''[[VideoGame/DanganronpaAnotherEpisodeUltraDespairGirls Ultra Despair Girls]]'', Fukawa has discovered she can also intentionally switch into Genocider Syo temporarily by zapping herself in the head with a taser; the more power she uses, the longer it lasts. Kids, don't try this at home!