Split-Personality Switch Trigger

"Lance, in his grief, disowned that side of himself. (But) when the bandanna comes up, he is once again certain and sure. He is the Outlaw Kid and his mind is clear and he knows what must be done."

— Dramatis Personae for Lance Temple, in Blaze of Glory

A Split Personality 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 anger as the trigger, but there are some that are more specific. Examples that are Played for Drama might have the trigger be associated with some episode of the characters' Dark and Troubled Past. Played for Laughs examples tend to make the trigger an Amusing Injury, particularly a bop to the head, which can even lead to the development of a split personality if the person doesn't already have one (but only in fiction). A Switch Trigger can also be added to the personality after the fact by a psychologist or the like, to help the afflicted person cope with their disorder better.

There are three ways this trope can be used, depending on what kind of Split Personality the person has:

1. The person is generally in one personality, but a specific stimulus causes them to switch to another personality.
2. The person is generally in one personality, but when they change into their other personality (or personalities), they can be switched back to their default state with a specific stimulus.
3. The person has no default personality, but one or all the personalities have specific triggers that cause them to appear.

Over the course of the story, the personality in question may become able to overpower the Trigger and stay in the driver's seat.

This is Truth in Television; real cases of DID are the result of severe trauma experienced in childhood, and as such, the factors associated with such trauma will cause the alternate personality to take over and protect the person from being reminded of their past.

Compare Trigger Phrase, a set of words that causes various effects on its target, and might be this trope if they have a Split Personality. Can overlap with Split-Personality Makeover or The Hat Makes the Man if the trigger involves changing the character's appearance.

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Examples:

Anime & Manga

• In the Funimation dub of Crayon Shin-chan, the normally sweet and shy (but still Covert Pervert) Miss Polly turns into a full-on dominatrix if you remove her glasses.
• Dragon Ball: Launch turns back and forth from a blue-haired kind-hearted Ditz, and a blonde-haired and violent "Kushami" form, whenever she sneezes.
• Excel♡Saga: Parodied in one episode in which a cute detective channels her late father whenever she puts on his hat.
• In Food Wars!, 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.
• GTO: The Early Years: 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 Yasha and attacks him after Eikichi revs his bike.
• In the Crossfire side-stories of 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.
• Kaede from How to Keep a Mummy becomes a creepy manizer when she puts glasses on. Kashiwagi calls her "Kaede-sama" when in this state.
• In Othello, the shy main character Yaya switches to her alter ego, bold and assertive Nana, when she sees her reflection.
• Kaere of Sayonara, Zetsubou-Sensei switches between her Jerkass and Shrinking Violet personalities whenever someone says "Go away".
• Yamamoto Jun from Special A turns from a relatively shy guy to The Casanova whenever he is kissed by a girl. Later on, it seems to be when a certain girl just looks at him.
• In the Not Safe for Work anime Sprite: Between Two Worlds, meek and submissive Shrinking Violet Manami turns into her assertive, self-confident alter-ego Nami whenever she hears the name Nami.
• Yu-Gi-Oh!: Marik's dark alter emerges whenever Odion is injured or unconscious.

Comic Books

• Batman:
  • Arnold Wesker is a strange example, playing out his Split Personality by way of ventriloquism. However, he can only do this if he's holding a puppet of his alternate personality, named Scarface. Some attempts to treat him have involved making him use a different puppet altogether, to varying degrees of success.
  • Batman's Ax-Crazy alter of "The Batman of Zur-En-Arrh" emerges when Bruce's regular personality (whichever one it is) is incapacitated. According to him, he's Batman without Bruce's influence.
• Blaze of Glory: Lance Temple becomes the Outlaw Kid if anyone pulls his bandanna over his face. In the final issue, he does that himself.
• The Incredible Hulk: Some, but not all, of Bruce Banner's alters can only come out at night. This includes Joe Fixit and Immortal Hulk. In the latter's own series, it's said to be associated with how much Banner fears and distrusts that particular personality: As they 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: Season One 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 Hand Wave. The regular 'Jade Giant' version of the character has the more popular trigger of 'anger'.
• Justice League International: After challenging Batman (and getting knocked out by a single punch), Guy Gardner hit his head upon regaining consciousness. The impact caused him to change from a hot-headed Jerkass to a sensitive poet. A Running Gag over the next few years involved Guy changing between these two personalities whenever he hit his head.
• Monica's Gang: Professor Spada turns into his Superpowered Evil Side, Doctor Spam, if he gets shoved into a computer. This is not an Amusing Injury, he literally gets shoved inside the computer if this happens. What exactly Doctor Spam is has never been fully explained, but it's described as a split personality.
• Suicide Squad: 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.

Fan Works

• Infinity Train: Knight of the Orange Lily: For some odd reason Specter has a Psycho Electro Split Personality named "Easter" — originally a play on "Earth-as-Specter" before Paul London shortened it. Gladion, London and Tokio assume that in order for Easter to come out to play they have to electrocute him. So Gladion has Silvally equipped with an Electric Memory do the deed. It works...and the group instantly regrets it. The only way for Easter to switch back to Specter is by London giving him a Tap on the Head with his staff.

Film - Live-Action

• The Court Jester: The cowardly Hubert is hypnotized to become a brilliant, brave swordsman whenever someone snaps their fingers and revert back to his original personality when someone snaps their fingers again. During the climactic battle, everyone keeps innocently snapping their fingers and Hubert yo-yos between the two personalities.
• In the MCU the Hulk would emerge whenever Bruce Banner got angry or physically hurt. He eventually learned to keep the Hulk from emerging in response to anger. Black Widow developed a way to bring Bruce back by speaking a soothing phrase.
• In Me, Myself & Irene, Rhode Island State Trooper Charlie, a Dogged Nice Guy everyone takes advantage of, develops a split personality named Hank Evans, a rude and violent Jerkass that emerges whenever Charlie is unable to deal with some external conflict. By the end of the movie, Hank is subsumed into Charlie once the latter becomes able to stand up for himself.

Literature

• Mr. Krupp of Captain Underpants is hypnotized into thinking he is the titular superhero. Specifically, he becomes Captain Underpants when he hears someone snap their fingers, and reverts back to Krupp when he's splashed with water. Hilarity Ensues, as that means anyone, including Krupp himself, can trigger his transformation into Captain Underpants, and when he's reverted back to normal, he's often upset to find himself soaking wet for reasons he's unaware of.
• Suzuho in Magician's Academy is usually quiet and meek, communicating only through 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.
• The Strange Case of Dr. Jekyll and Mr. Hyde: In this Trope Maker for split personalities in fiction, Dr. Jekyll creates the persona of Mr. Hyde by ingesting a potion that makes all his negative qualities to come to the forefront. Jekyll becomes worried when he realizes he's becoming Hyde without the potion, and even more when he starts running out of the potion altogether. Realizing he'll soon become Hyde permanently, Jekyll chooses to kill himself and spare the world of his inner demons.
• In Super Powereds, Hershel and Roy originally switched out uncontrollably. The mysterious procedure that the Superpowereds went through fixed it so that Hershel is out by default and Roy comes out when he/they drink any whiskey.
• In When the Bough Breaks (part of Mercedes Lackey's SERR Ated Edge series), a young girl develops multiple personalities when her father starts raping her. One personality takes over whenever she realizes a rape is about to occur, to protect the other personalities from knowing what's been going on.

Live-Action TV

• In the Batman (1966) series, Professor William Omaha McElroy, an Egyptologist at Yale University, would become the villain King Tut every time he was hit on the head and return to normal when he was hit on the head again. He became the only series villain never to be sent to jail, via the insanity defense. Prof. McElroy also knew about his Tut self (despite not recalling what he did under it) and also tried to prevent King Tut's emergence via wearing a special hat supposed to soften blows to the head. Obviously, it didn't work.
• On Buffy the Vampire Slayer the First Evil programmed Spike to become a mindless animal in response to a particular song.
• On Charles in Charge Charles would become Chaz Lamborghini whenever he was stressed and got hit on the head.
• Deconstructed with Mary Walker in Iron Fist (2017) 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 Zaitsev Plus One, the main character Sasha Zaitsev has three things that can trigger a switch to his cynical and womanizing alter, Fyodor: being hit in the head, blinded by a bright light, or deafened by loud noise.

Tabletop Games

• A possible gameplay mechanic in GURPS if you create a character with DID. Are you in a stressful situation? If yes, roll the die. Failed the roll? Switch to another personality. It's not all bad; your alters have different stats and skills from you, so just like many examples of DID in fiction, they may be better suited for the situation at hand. However, the trigger applies to all of them if you have more than one, so if you fail the roll, it's anyone's guess which one is going to take the reins.

Video Games

• Elite Beat Agents: Jack turns into an overconfident daredevil whenever he presses a button in his taximeter. Pressing it again causes him to revert back to his shy and apologetic self.
• The Fallout: New Vegas DLC Dead Money has the character Dog/God. The 'Dog' personality emerges when God hears a recording of Elijah's voice, while 'God' surfaces if Dog hears a recording of God's voice.
• Fire Emblem:
  • Fire Emblem: Awakening: Noire started off using a talisman to change into her Ax-Crazy alter, but it's implied to be little more than a Magic Feather. Tharja, her mother, takes the talisman from her, after which it becomes clear Noire can still trigger the switch herself (though she doesn't have as much control of it as she might want to).
    Tharja: See. No daughter of mine needs some mummer's prop to be strong.
  • In Fire Emblem: Three Houses, Constance's personality switches depending on whether she is exposed to sunlight. Out of the sun, she is a haughty Large Ham. Under the sun, however, she becomes a sullen Shrinking Violet.
• Galaxy Angel II: Kahlua Marjoram turns into her Sexier Alter Ego 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.
• Goonya Monster's Clione is normally gentle and timid, but as soon as he yawns, that's when his more outgoing and carefree personality comes out.
• Senran Kagura: Ryouki switches between a extremely nice Cool Big Sis figure to a loud- foul-mouthed delinquent if anyone touches her halo, and reverts back to normal if the halo is touched again.
• Super Robot Wars: Aschen Brodel from Endless Generation is an android with a split personality. If her body temperature raises high enough, Code DTD activates and changes her personality from a stoic Robot Girl to an excitable Genki Girl. And makes her outfit more stripperific for some reason.
• Tokyo Mirage Sessions ♯FE has a Show Within a Show called 'Sneeze Detective', which Tsubasa stars in at one point. The titular character has a blonde, Jerkass split personality that comes out when she sneezes, hence the name.

Visual Novels

• Danganronpa: Toko Fukawa switches between her Serial Killer alter of Genocide Jack and back when they either sneeze or fall unconscious. By 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!
• In Sunrider Liberation Day, Asaga develops one as a by-product of overusing her Super Mode, and as such, using her powers becomes the trigger for her new Knight Templar personality.
• Uta No Prince-sama: The docile and kind Natsuki has a split personality named Satsuki who is the exact opposite of him — a hot-tempered jerk. Satsuki comes out when Natsuki's glasses come off.

Webcomics

• In Homestuck, saying the name of Calliope or Caliborn's other personality to the one in control causes them to fall asleep and for the one whose name was spoken to wake up. The name is not used until one of them has killed the other (by having their dream self assassinated), making it ineffective.
• In Jix the title character's Mad Scientist personality Lamerix is triggered by her goggles, while the superhero persona The Ambis needs their custom armor to take control. Their reliance on physical totems probably explains why those personas eventually got subsumed into the "core" personalities of Jix and Remula respectively.
• League of Super Redundant Heroes: Good Girl turns into Bad Good Girl whenever she takes off her halo, and returns to her original personality when the halo comes back.

Web Original

• Jake and Amir's Running Gag that Jake becomes the unhinged one where fashion and girls are concerned is occasionally activated in mid-episode. Particularly visible in "Celebrity Date" when, after scoffing at Amir's plan to date a celebrity in order to socially succeed in LA, he finds out that Amir has apparently managed to get Amanda Bynes' number through typically underhanded means.
  Jake: Jesus, dude. (whipping on a straw hat) Why didn't you tell me you had an in with Bynes? (horrifying sleazy cackle, Maniac Tongue) She's All That!

Western Animation

• In Batman: The Animated Series, before becoming Two-Face, Harvey Dent would become Big Bad Harv whenever he was angry. His psychiatrist was able to trigger a switch with hypnosis, then a switch back with a snap of her finger.
• In Beavis and Butt-Head, The Great Cornholio makes his appearance whenever Beavis has too much sugar and/or caffeine, and when he comes back to himself (usually in some awkward situation), he doesn't remember Cornholio's actions.
• In The Flintstones, Fred has a bowling ball dropped on his head and becomes a haughty, pretentious upper-class snob who insists on being addressed as "Frederick", driving Wilma, Barney and Betty up the wall. At the end of the episode, another head injury returns him to his usual grouchy, slovenly self.
  • This would be referenced decades later in Harvey Birdman, Attorney at Law, where this is used to explain why Fred became a Tony Soprano-esque mob boss.
• In an episode of Teenage Mutant Ninja Turtles (1987), Shredder thinks he's Michelangelo after getting zapped in the head with a laser; saying the word "Shredder" makes him realize he's really Shredder, but saying Michelangelo makes him think he's Michelangelo again.
• Mike from Total Drama has DID. Revenge of the Island introduces four of his additional personalities, each activated by a specific stimulus: he turns into Chester when irritated or agitated, into Vito when he takes off his shirt, into Svetlana when he has to use acrobatics in the challenges and into Manitoba Smith when he puts on a hat. He reverts back to Mike when Zoey is in danger or somebody calls his name. Additionally, Mike can also change back from Vito and Manitoba by putting a shirt back on and removing the hat respectively.

Real Life

• Jeni Haynes, 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.
  Symphony (after taking control on the witness stand): Hello, I'm Symphony. Jeni's gotten into a pickle, so I've come tell you all about it if you don't mind.

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