Split-Personality Takeover

"I'm saying... I'm saying I'm an insect who dreamt he was a man and loved it... but now the dream is over, and the insect is awake."

— Seth Brundle, The Fly (1986)

After months or years of suffering a Split Personality, Enemy Within, or Superpowered Evil Side, the character is cured! ...by having the weaker, "sane" personality lose all control over the body to their inner evil. Like the slow erosion of a mountain, Jekyll has succumbed to Hyde's implacable id-like force, leaving nothing but the shell of who they were.

This isn't just an identity crisis or something that can be wished away with good intentions, at least not easily. This is the permanent and literal death of a person — or at least a personality.

This is especially common if one personality is more dominant than the other, or the "good" personality is subject to Mind Rape or a Heroic BSoD. Occasionally, a truly strong-willed "good" personality can do the takeover — although it's likelier that they'll choose to "merge" or reintegrate with their evil side into a "whole" personality because Good Is Impotent.

If the takeover is incomplete, expect to see signs that the original is Fighting from the Inside. Antonym to Split-Personality Merge. Compare and contrast with Copied the Morals, Too, where some sort of evil clone or knockoff of a heroic character somehow inherits the heroic character's morality, much to the detriment of the villain's plan. When this is induced by outside brainwashing, it may be Brainwashing for the Greater Good.

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Examples:

Anime & Manga

• Subverted in Ah! My Goddess. Belldandy's sister, Urd, being half-demon and half-goddess, forcibly has her good and evil halves split apart by Mara, and when they are rejoined, she finds that her demonic side is slowly slipping away, which would eventually result in her becoming a full-blown goddess. However, Keiichi and her sisters refuse to let the Urd they've come to know disappear, so they summon the only person other than the Almighty One (whom they assume won't help them since he would rather Urd become a total goddess) with enough power to safely return Urd to stable demon/angel form — the ruler of all demons and her mother, Hild. It works, but they accidentally end up convincing Hild to leave a portion of herself behind on Earth to torment them along with Mara.
• Subverted in Angel Beats!, where Tenshi manages to win out against dozens, if not hundreds of murderous versions of herself after all of them recombine into one person. Given her exhausted state when it happened, and Key's tendency to Kick the Dog, it was a close call.
• A variation occurs in Elfen Lied as Lucy's good personality takes over the evil (if tragic and even pitiful) one but neither personality is okay with the omnicidal maniac side taking over at the end of the manga, leading to a Shoot the Dog moment from Kouta.
• In Animerica, this occurs to Kiyone, explaining his Magnificent Bastard actions in Season 2. The "evil" side attempts to do this again in the beginning of Season 3, but thankfully it gets destroyed for good this time.
• In Saint Seiya, the Big Bad of the first major plot arc is Saga, Gemini Gold Saint, a saintly (forgive the pun) warrior in Athena's service, whose Split Personality is thoroughly and irredeemably evil. Naturally, it takes over for good, which results in the Sanctuary War, although Saga's good side still shows occasionally (if only to have an Heroic BSoD at his own actions.)
• This is why Moka never takes off the rosary herself in Rosario + Vampire: the outer Moka would be replaced by the inner Moka forever. This doesn't stop her from trying it anyway.
• Marik and Dark Marik from Yu-Gi-Oh!. The split personality was born when Marik's father carved his back. The pain was so severe that Marik created a second masochistic personality to cope with it. Dark Marik took control to kill his father a year later and intended to do away with the rest of the family, but he retreated back into Marik's subconscious due to his Morality Chain adoptive brother, Rishid (Odion in the anime dub). When Rishid falls unconscious, Dark Marik takes control and nearly succeeds in killing Marik for ownership of his body.
• Bleach: Hollow transformations consist of the original personality of a Plus being largely destroyed in favour of something created from raw instinct. The effect is permanent; even if a Hollow can resist the effect (such as Sora), it's only a temporary measure at best. The effect does lessen as a Hollow goes through its stages of evolution as a Menos and their personality reverts closer to their original as their never-ending hunger becomes sated (Adjuchas and Vasto Lorde level, as well as becoming an Arrancar), but that takes a long time and a lot of devoured creatures to get to. And when that happens, there's no guarantee that it'll be the original soul that will be in control of the Menos. It's possible for any of the other souls that a Menos has devoured to take over from the inside and become the dominant personality, if it's strong-willed enough.
  • Ichigo is a special case, as his Hollowfication happened during his training for Shinigami powers. He did eventually learn how to control his Hollow powers; and in the final arc, it's revealed to be the basis for his shinigami power and his zanpakutou's sealed form.
• Goes the less common direction for Riff in Count Cain, who was given a nice personality in order to gain Cain's trust, which then faces off, and wins, against the original evil one.
• Pretty Sammy quotes this trope to Misao which it encourages her to help her in getting rid of Ramia's evil influence over her.
  Even if you stay as Pixy Misa forever, I'll still really love you, Misao!
• In Psyren, when Amamiya is shot Abyss, her other personality created from her suppressed emotions takes over momentarily.
• Played with in Samurai Deeper Kyo. In the manga version, Demon Eyes Kyo is a legendary killer whose mind has been sealed inside the body of Mibu Kyoshiro, but occasionally rises to the surface. In the anime version, Demon Eyes Kyo is the dark side of Kyo's personality that escaped and became an Enemy Without, then was reabsorbed back into Kyo. In both versions, Kyo eventually assumes full-time control of Kyoshiro's body.
• Inuyasha:
  • Although Naraku already dominates Onigumo, he plans on removing his heart from him since his love for Kikyo prevents him from hurting her.
  • A more classic example comes from Inuyasha himself: whenever in the presence of a powerful demonic aura and/or separated from his sword Tessaiga, his demon blood takes him over and he transforms into his fully demonic form, then proceeds to wantonly murder anyone nearby. It takes an increasingly large amount of effort to bring him back to normal each time.
• Fullmetal Alchemist:
  • Bradley's body's original owner was bound to a Philospher's Stone and waged a war with the various personalities trapped inside the Stone until the current Bradley became dominant. Even he's not sure whether he's the original test subject or some other personality.
  • Averted with Ling/Greed, which started off this way but ended up as more a case of Symbiotic Possession because Ling willfully gave in and thus serves as The Conscience to Greed.
• Shiro in Deadman Wonderland seems to have had her violent side take over. Chapter 55, however, reveals that this is Averted, as her supposed Split Personality never existed in the first place. She is incredibly jealous of Ganta for being able to live a comfortable life she never had as a result of being his replacement and was doing everything in her power to make sure he was strong enough to kill her.
• In W-Change!!, the heroine is a sweet airheaded girl who has an incredibly violent persona that surfaces whenever she falls unconscious. Halfway through the series, her "dark side" took over as her main personality.
• In Digimon Ghost Game, it's revealed that the sadistic and merciless GulusGammamon was the original personality, and kind and childlike Gammamon that is seen throughout the series was a split personality that manifested and took over under unknown circumstances. GulusGammamon also attempts to pull this off in Episodes 66 and 67 to reclaim control, but due to the interference of Hiro, he fails and is absorbed into Gammamon fully.

Comic Books

• In Batman: The Dark Knight Returns, Harvey Dent has received surgery to repair his face's damaged half, but it has the opposite effect on his mind — Two-Face is now entirely in control.
• In Buffy the Vampire Slayer, it's shown that Oz came very close to going down this road willingly. He had been trying to deal with his werewolf side for a relatively long time, only to learn that whatever he tried was pointless and whatever ground he had gained before was lost. Eventually, giving in and simply being done with it all started to look very tempting. It's never explicitly stated why he didn't go through with it, but his words "But I didn't" are coupled with an image of Bayarmaa, his future wife and mother of his son.
• Daredevil: This is Bloody Mary/Typhoid Mary's entire schtick. She has rather impressive psychic and telekinetic powers, but she also has a horrible case of disassociative identity disorder; namely, at least nine of them. Two of them (the aforementioned Bloody/Typhoid Marys) tend to take over more often than not, and there have been at least two instances where one or both have "permanently" taken over only for later events to unlock her original (non-powered) personality once more.
• A horribly tragic case occurs to Dan Turpin during Final Crisis. To be fair, it skirts between this and Demonic Possession, but after visiting Bludhaven in search for missing children, Danny starts getting blackouts and finds that he can't control himself after a certain point. He then discovers with horror that he is being possessed and/or erased by Darkseid. After he is completely possessed, he is poisoned by Batman, nearly killed by the Black Racer, and finally and utterly destroyed by Superman. The final issue implies, but never outright states, that it's only Darkseid who is destroyed and that Turpin is ultimately freed. It's probably a moot point now that DC has reset the universe again.
• The Incredible Hulk:
  • Betty Ross is in constant risk of this when she becomes Red She-Hulk.
  • This is the reason why Doc Samson turns evil in Hulk (2008). He developed another set of personalities — his current persona, the identity of Doctor Leonard Samson PhD, and the more ruthless 'Samson' — and a 'psychiatric evaluation' in his own mind organized by M.O.D.O.K. saw Samson kill the other two.
  • The Hulk himself would like nothing more than to rid himself of "puny" Bruce Banner once and for all, as much as Bruce Banner wants to rid himself of the Hulk. Several iterations have tried, particularly Joe Fixit, and succeeded for extended periods of time, but one way or another Bruce Banner always resurfaces eventually.
  • Inverted, to some extent, with the Hulk's son Skaar, where the weaker, more vulnerable personality ('puny' Skaar) has recently managed to escape Skaar's suppression of him in their shared mind.
  • The events of Immortal Hulk come about from one of these. After Bruce's repeated deaths over the previous few years, a new Hulk personality appeared... at which point the titular Hulk of this series got lose, tore that one into shreds and took over control over the whole thing. To protect Bruce. Later on it turns out the other alters are only allowed out on his say-so (or in the case of the Savage Hulk, if he loses control enough). It's partway through the series it turns out this newer Hulk is the Devil Hulk.
  • This has happened to the evil future version of the Hulk called the Maestro from The Incredible Hulk: Future Imperfect. There's no more Banner, no more Hulk, or Joe, or any of the others. It's just the Maestro now.
• This is what causes Brainwave's initial Face–Heel Turn after the end of Infinity, Inc.. About fifteen years later, the new personality is possessed by a ''third'', also villainous, personality. Eventually, when the third personality is defeated, it's heavily implied that it ate the second one. In any case, he gets better.
• New Mutants: Legion often runs the risk of this. In his first full appearance, the team are dragged inside his mind, where there's a battle going on between two alters (rogue Jerkass Jack and volatile pyrokinetic Cyndi) and another person who got dragged inside David's mind years ago. It eventually turns out to be an inverted case; the alters are battling against being erased, while the guy is trying to heal David's shattered psyche. The next time David reappears, Jack violently seizes control, tries to murder Moira MacTaggert and Wolfsbane, and runs off to hit the nearest bar and get some action. Part of the problem the New Mutants have is they want to restore David, but have no idea on how to do that.
• This happens to Professor X in Onslaught as the title villain is Xavier's dark side merged with the basest parts of Magneto's and run amok.
• Spider-Man:
  • While it wasn't made as big a deal of as the animated version, it used to be that the Goblin Serum gave Norman Osborn a Split Personality, and would periodically forget that he had a Superpowered Evil Side and go back to being an industrialist. Since he came Back from the Dead, it seems to be accepted that he's the Goblin all the time. Though during his time on Thunderbolts and Dark Reign, it seems the split personality explanation is back. Subverted in that Osborn is still an evil jerk, the Goblin is just his darker side. At the end of "Goblin War", the Goblin formula is flushed from his system, and he declares that Spider-Man has never faced a Green Goblin who's sane before...
  • One story arc involves Symbiote knockoffs. Venom, of course, always refers to himself as 'We' (as in, Eddie Brock and his Symbiote), so when one of the symbiotes stops talking in plural, Spidey knows that she's all gone — the Symbiote has taken over her mind. An interesting conclusion of this is that the very thing that makes Venom sound like a raving lunatic is actually an indication of his remaining sanity — or even a psychic crutch necessary for him to retain his identity.
  • During the storyline The Gauntlet, Curt Connors' worst fears are realized when he loses a battle of wills with the Lizard part of his psyche. The Lizard kills and eats Curt's son Billy, and "Curt" essentially dies due to the trauma, leaving only the Lizard. A later story reverses this: Spider-Man manages to bring Curt's body back but doesn't realize that it's still the Lizard's mind. Then the Lizard reverts to his usual form, but this restores Curt's mind. Curt keeps this quiet because he feels he deserves to be locked up.
• This happens to Moon Knight in Ultimate Spider-Man. Doubles as a case of Becoming the Mask, since the personality that takes over was created specifically to be more evil and violent.
• Wonder Woman: In Silver Age DC Comics, Priscilla Rich's jealousy and envy of Wonder Woman caused her to spawn a second personality. As the Cheetah, she became a recurrent foe in the Sensation Comics and Wonder Woman (1942) series.

Fan Works

• Pony POV Series:
  • Discord originally entered the mortal world as an innocent version of himself named Dissy who had none of his evil self's memories. Sadly, Discord's original persona still existed and eventually began to awake until it finally devoured Dissy and began his thousand-year reign. It's mentioned in-universe this happening was unique to Discord, as most deities instead have a Split-Personality Merge in situations such as this. However, later it turns out Dissy still exists and begins to resurface during the Rumors Arc to aid the heroes. In the end, Discord, after a Heel Realization, allows Dissy to do this to him, resulting in the original Discord being Deader than Dead and Dissy reincarnating through Pinkie Pie.
  • A benevolent version happens with Minuette, who's actually the Master using a fob watch. While her evil persona spends the arc attempting this trope, eventually Minuette manages to destroy the Master by feeding his fob watch to the Blank Wolf, allowing her to take his place fully.
• The dark side of Socrates attempts this in Calvin & Hobbes: The Series, as his transmitter chip has fused with his mind, allowing the dark version to try and take over the land inside his head. The protagonists stop him, of course.
• In Weight of the World after Remnant nation-tans are reborn and reach a certain age, they’ll remember who they really are and their nation memories and personality will take over, erasing the human personality they had before that point. According to Word of God, if the human identity is different enough, at most the nation-tan will get two Semblances for that life. Other than that, the original human personality is completely gone, as confirmed by Neo/Mistral in the sequel The Shattered Soul.
• In "Two For One" of the Danny Phantom Facing the Future Series, Danny ends up inside his psyche where he encounters his ghost half, which actually has a consciousness of its own, and, tired of Danny treating him like a burden, attempted to take over his body. Fortunately, Danny managed to convince his ghost half that he needed his humanity, otherwise, he'd end up as Dark Danny. This resulted in the pair doing a Split-Personality Merge which allowed Danny to get control of his True Ghost Form.
• Getting Lost in the Con has Frank Fontaine's ADAM injection result in the creation of a split personality modeled after his Atlas identity, who does not approve of Frank's plan to turn himself into an ADAM monster to kill Jack. The split eventually manages to take over Fontaine's body just in time to stop the full ADAM injection process and allow Jack to kill him to leave Rapture.

Films — Animation

• More of a Split-Personality Removal, but in The LEGO Movie, there's Bad Cop, who shares a body with Good Cop, whose face is on the other side of their head. When Bad Cop refuses to test the Kragle on his own parents, Lord Business decides that Good Cop has made him weak and removes Good Cop's face with nail polish remover and a cotton swab. However, Good Cop's influence isn't completely gone, as Bad Cop later has a Heel–Face Turn and attempts to draw a new Good Cop face on the other side of his head with a marker.

Films — Live-Action

• Cleo Leo: Initially 'Cleo' has an internal monologue in Leo's masculine voice indicating that the reincarnation is purely physical. As the film progresses and 'Cleo' adapts to life as a woman the 'Leo' mental voice begins to become fainter and interspersed with an internal voice in Cleo's feminine voice with 'Leo' expressing resentment, anger and reluctance to change while 'Cleo' expresses confusion but also acceptance and femininity including attraction to Bob. Eventually, half way through the movie the 'Leo' voice fades away completely leaving just 'Cleo' as she begins to think of herself as a woman.
• The ending of the movie Identity has the most evil of Malcolm Rivers' personalities, the one who turned him into a serial killer, killing the last of the alternates to be the only one remaining in the body.
• At the end of Psycho, it is revealed that Norman Bates developed a dissociative identity disorder after he murdered his jealous and abusive mother ten years ago. Unable to cope with his guilt about the crime, he recreated his mother in his own mind as an alternate personality, which took over in moments of emotional distress and caused him to kill any woman he felt attracted to. The final scene shows Norman in a jail cell while an internal monologue in his mother's voice can be heard, showing that the dominant "mother" personality now has complete control over his body.
• In the remake The Fly (1986) Scientist Seth Brundle slowly transforms into a pathetic and diseased human-fly hybrid after accidentally fusing with said-insect in a teleporting experiment. At first, the deformities were purely physical, as his human flesh warped and decayed into a "cocoon" under which the monster grew. Sadly, he also transformed on a mental level into an instinct-based animal, unbound by compassion and morality. The love of Veronica, our heroine, was sadly not enough to stop his predictions from coming true...
• Averted in the sequel The Fly II with Brundle and Veronica's son Martin. The murderous rampage against his oppressors is all him, as shown where he actually goes out his way to avoid harming a dog and sparing his Love Interest Beth Logan, implying that his mind has largely remained unchanged despite his body's transformation. Said oppressors are bad enough that this isn't a Moral Event Horizon for Martin.
• In Fight Club, this is claimed by Tyler Durden to be the evil plan all along. The Narrator disagrees and kills Tyler before it happens.
• The VERY heavily fictionalised film of The Boston Strangler implies something like this at the end. The killer, Albert De Salvo, has been diagnosed with Multiple Personality Disorder (the real life De Salvo was never even suspected of having this condition,) and the film ends with him apparently having gone permanently catatonic after re-enacting one of the murders under the influence of his murderous side, and with no sign of the gentle family man left.
• In X-Men: The Last Stand, Jean Grey Came Back Wrong and awakened the dormant Superpowered Evil Side Phoenix, who manifests more often than not, usually causing quite the damage in the process.
• In the "Ventriloquist's Story" in Dead of Night, ventriloquist Maxwell Frere (Michael Redgrave) smashes up his puppet/Demonic Dummy "Hugo" (who, it is strongly implied, channels Maxwell's own Split Personality) after "Hugo" tauntingly threatens to join Maxwell's rival ventriloquist. Maxwell is placed into a mental institution and goes into a catatonic state until his doctors bring in the rival ventriloquist to try and give him a jolt. Upon seeing the rival, Maxwell smiles and opens his mouth, but the voice that comes out of his throat (his lips remaining unmoving) is that of "Hugo".
• In The Two Faces of Dr. Jekyll, Hyde tries to enforce this by framing Jekyll for his crimes, knowing that the doctor will have to cede control to him lest he be a hunted fugitive.
• Marvel Cinematic Universe:
  • In Thor: Ragnarok, Bruce Banner fears that the Hulk is starting to do this. After he had to transform to help fight Ultron, Hulk maintained control of their body for two years while they were stuck on Sakaar, with Bruce being totally unaware of any time passage. When Thor notes that the team may need Hulk to take back Asgard, Bruce refuses the idea vigorously because he's not sure if he'll ever turn back again. Ultimately, he's forced to take the risk and Hulk out in order to defeat Fenris.
  • His very next appearance, Avengers: Infinity War, turns this on its head - Hulk refuses to come out, even when Bruce wants him to, after being beaten into submission by Thanos.
  • The reverse of Bruce's fear is actually realized in the next appearance after this, Avengers: Endgame he remains in Hulk form for the entire film, but retains Bruce's mind, a state both are happy with.
• Upgrade: By the end, STEM, that had up until that point been a voice that could sometimes take over Grey's body, takes full control and traps Grey's mind in a Lotus-Eater Machine.
• Split: Kevin Wendell Crumb has twenty-three distinct personalities, the most benevolent one is called Barry, but several of his personalities are trying to bring out a dangerous Ax-Crazy 24th personality called the Beast. Late in the film it's revealed that all of his personalities have been keeping the original Kevin personality suppressed for two years.
• Asylum (1972 Horror): In "Lucy Comes to Stay", Barbara has just been released from hospital and brought home by her brother George. She encounters her 'friend' Lucy, who appears (to the audience) to be an Imaginary Friend. However, as Lucy commits a series of acts, culminating in the murder of George and Nurse Higgins, it seems that she might be a Not-So-Imaginary Friend. But when Dr. Martin interviews her in the asylum and asks where Lucy is, Barbara points at the mirror, and when she looks into it, she sees Lucy's reflection looking back at her.
• In The Nutty Professor (1996), Buddy Love begins as merely a slimmer, more confident alter ego for the heavyset Professor Sherman Klump. However, after a while, Buddy becomes another personality of his own and tries to do this to Sherman. This leads to a particularly intense struggle between the two personalities, where Sherman wins and Buddy is subdued.
• Malignant has Gabriel, who was a parasitic Evil Twin and after his surgical removal, becomes an evil voice inside Emily/Madison's head, with the power to manipulate her visual cortex so Madison does not see that she's doing until it's too late. And after being reawakened, he finds out how to possess her body and go on murder sprees, with the ultimate endgame being to be the true host.
• Double Trouble: Played with. Florian, who is gentle and kind but also a spineless wimp, develops a split personality: Eugene, an aggressive, alpha male businessman, and also a babe hound and corrupt criminal. The closing title cards specifically state that the persons of Florian and Eugene blended. New Florian is still a fundamentally decent fellow who wins Elizabeth's hand in marriage, but he as enough of Eugene's confidence and aggression in him to tell Eugene's gangster business partners to get lost when they show up again.

Literature

• The Strange Case of Dr. Jekyll and Mr. Hyde: This happened to Dr. Jekyll at the end of his strange case. Luckily for Victorian England, Jekyll locked himself up before changing completely and ultimately committed suicide.
  "This, then, is the last time, short of a miracle, that Henry Jekyll can think his own thoughts or see his own face (now how sadly altered!) in the glass."
• In a rare case of the good side taking over (with a little help), from Gene Wolfe's story "The Death of Doctor Island", the psychotic teenager William, whose brain has been surgically divided between the left and right hemispheres, is deliberately subjected to a devastating trauma which leaves him catatonic. This allows his previously helpless right-brain personality, the calm and placid "Kenneth", to take control of his body.
• Artemis Fowl:
  • Happens in The Lost Colony, when after Artemis and Co. escape from the Time Crash that's about to happen on Hybras, Qweffor (assisted by N°1) does it to the Big Bad Abbot.
  • Happens again in The Atlantis Complex. Artemis, having the titular disease, is taken over by his alter, Orion, multiple times.
• Happens to one of the bad guys in Shade's Children: When the titular Knight Templar Virtual Ghost uploads himself into a supercomputer, his conscience becomes personified in Robert Ingman, who is, coincidentally, Shade's original identity. As with the trope, Robert eventually destroys his dark side and helps the protagonists banish the local Dimension Lords. Too bad the other rule about redemption is played quite straight.
• In The Lord of the Rings, the character Gollum's darker side of his personality ultimately ends up taking control over his kinder side.
• Came this close to happening to Tahiri/Riina from the Star Wars: New Jedi Order series. Riina was not "evil", per se- though extremely messed up, she had a Pet the Dog in one of the few times she actually did manage to seize control of their body, and the merge helped Tahiri regain her sanity largely because each compensated for the other's issues (Riina's acceptance of pain and death helped Tahiri get past her emotional fragility following her boyfriend's death, while Tahiri's moral center held back Riina's more violent urges).
• In The Pilo Family Circus, this happens to every single clown employed by the circus, due to prolonged use of the magical facepaint they wear: it takes around two years of usage for the new personality to completely merge with the clown's brain, but since the facepaint also grants the user superhuman strength, a newly-recruited clown has to wear it just to survive the early months at the circus, and by then, the clown's addicted. Jamie, the novel's protagonist, only just manages to avoid this fate.
• This happened to a teenager named Saxon Hyde at the beginning of Michael Slade's Ghoul. That's especially unfortunate, because Saxon was the only one of this young man's personalities that wasn't a serial killer.
• The first half of the Dragonlance: The New Adventures series consists of an evil wizard trying to engineer one of these. He implanted the preserved spirit of a powerful evil sorceress in one of his mindwiped servants to try to access her magical knowledge once she took over the servant. Needless to say, the sorceress is rather pissed when she does take over.
• In Zen and the Art of Motorcycle Maintenance the Narrator first tells us that Phaedrus has been killed by several thousand volts to the head. However, throughout the Chautauquas, it becomes clear that Phaedrus is alive and kicking and trying to gain control. Slightly different from the others, as it's the narrator's personality, the sane personality, that is the real takeover.
• In Stephen King's short story "Secret Window, Secret Garden," Mort Rainey's alter ego John Shooter claims Rainey "took the coward's way out". He briefly reverts to Rainey, but only after being shot.
  • King likes this trope; the same effect befalls Jack Torrance in The Shining and the whole town of Haven in The Tommyknockers.
• Robert Ludlum's The Bourne Supremacy features the Jason Bourne persona forcibly suppressing the civillian identity, David Webb, whenever they need to focus on doing something that requires his particular skillset or way of thinking. Later in the book, Bourne completely takes over as 'Delta', the insane version of David Webb that led Medusa into battles in Vietnam, in order to violently break into the sterile house. Fortunately Marie is there to bring Webb back to the surface.
  "David Webb had disappeared, only Jason Bourne remained. Yet he was both more and less the hunter of Carlos the Jackal. He was Delta the predator, the animal wanting only vengeance for a priceless part of his life that had been taken from him once again"
• In Fight Club, the Narrator spends the story slowly succumbing to his intense, charismatic dissociated identity Tyler Durden. Ultimately, the Narrator is Driven to Suicide in order to stop him.
• The Fate Worse than Death of Olivia from Hive Mind (2016). As a telepath, she had to deal with the people she read sticking in her mind. Most telepaths eventually figure out how to clear these "echo personalities" out, but she never did, so she ended up drowning under them; by the time she appears in the story, the original Olivia is essentially gone. One of her new personalities has fully taken over and started a terrorist cell, hoping that the treatment once she/Olivia is found out will let her fully eject the original Olivia and other echos and be the only personality.
• In Dune, the "preborn" (children exposed to the spice melange in the womb) are at high risk of having their minds swamped and erased by the ancestral personae and memories they are born with. And, in fact, this happens more than once:
  • Alia Atreides ends up taken over by the mind of her late grandfather Baron Harkonnen.
  • In order to be sure of ruling competently and setting mankind onto the Golden Path, Paul's son Leto II consciously gives up his own mind, allowing his tyrannical but wily ancestor Harum to administer a virtual "council" of personalities in his head.
• Skulduggery Pleasant has a couple:
  • Valkyrie suffers this from Darquesse, her Superpowered Evil Side, as the latter gets more powerful. Ironically, she'd had her True Name sealed to try and prevent this or being compelled to become Darquesse after seeing a Bad Future where Darquesse killed her parents along with practically everyone else. Unfortunately, a brief case of possession opened the door for the personality in question to get loose, which she also did when something rummaged around in her head or when Valkyrie was near death (which Valkyrie once exploited to fight Lord Vile). After that, she started whispering in Valkyrie's head more and more, finally refusing to come out when Valkyrie was being literally ripped apart and mentally torturing her into giving in.
  • Skulduggery has to deal with this risk with Lord Vile, a split personality formed out of immense trauma and rage that bound itself to his latent talent for necromancy. While he buried Vile centuries ago and became The Atoner, further trauma and proximity to the armour means the personality subconscious reanimates the armour (which nearly kills him). He is ultimately forced to become Vile again by putting on the armour as a Godzilla Threshold on more than one occasion, and while he manages to put him back in his box, he makes plain that every time he puts on the armour there is a very real chance that he may not come back and will have to be stopped by force. This isn't exactly easy, either: prior to the rise of Darquesse, Lord Vile was arguably the most feared sorcerer in history, even more so than his former master Mevolent (the Leibniz Universe implies that Vile was actually more powerful, and shows that Mevolent is surprisingly Affably Evil with plenty of human qualities. Aside from the odd Quizzical Tilt, Vile has none whatsoever), and it takes a True Name sorcerer or Mevolent himself to even have a prayer of beating him - and one of the two True Name sorcerers we see is a pacifist who makes sure to hide the armour, admitting that Vile's combination of sheer power, skill, and killer instinct could very possibly kill him, while Leibniz Vile beats Mevolent when they fight.

Live-Action TV

• Babylon 5: This is basically what happens to Talia in "Divided Loyalties". There is also a rogue telepath in one episode who goes through this.
• Buffyverse: This happens to Angel whenever Angelus is unleashed.
• In an episode of Criminal Minds, a young man's murderous and until-then unknown alter ego permanently takes over his body, in an attempt to protect him. In a twist, the alter ego that takes over is female.
  Dr. Reid: I am looking for Adam.
  Amanda: Just because you caught me doesn't mean you'll find him. You're not that smart.
• In Death Note, Mello starts off as a darker split personality of Near, kept mostly in check. Towards the end, Near collapses, and Mello takes over, complete with Evil Costume Switch.
• Doctor Who: In "Nightmare in Silver", the Doctor has to fend off the Cyber-Planner that calls itself Mr. Clever when it attempts to take over his mind. Seeing Matt Smith Acting for Two in a Sméagol/Gollum type fight is equal parts awesome and hilarious, with a touch of bone-chilling sinister thrown in by the episode's author.
• Played with in Farscape. Thanks to Scorpius' neurochip, Scorpius' "neural clone" gets stronger and stronger within Crichton over the course of the second season... until taking over completely in the finale. Even after surgery removes the chip itself, the neural clone, "Harvey", never really disappears. Once the chip is removed, though, Harvey loses any power he had and is basically trapped in John's head forever, with John able to shut him up whenever he wishes. The best Harvey can do to John is be mildly irritating — unless his life is in danger, in which case Harvey can muster up just enough power to be dangerous. In the "Peacekeeper Wars" miniseries, Harvey finally dies for good when the wormhole knowledge is deleted from John's brain.
• In The Flash (2014), this happens to Caitlin Snow, who gets taken over by her Killer Frost personality if she uses her powers.
• This happens repeatedly to Nikki in Heroes when her Superpowered Evil Side decides to start acting up.
• In the "One Last Prayer" episode of HBO's 1980s anthology The Hitchhiker, a pretty and talented singer called Miranda invents an image for herself guaranteed to succeed, but finds it starting to take over. She fights back, but The Bad Girl Wins.
• Jekyll: When Klein & Utterson finally manage to capture Dr. Jackman, they put him into a device that deletes one of the two personalities. Unfortunately for Jackman's wife, Hyde is the surviving personality. However, when Mrs. Jackman and her children are captured due to Hyde's immaturity, he resurrects his dead alter-ego and merges with him, mixing Hyde's incredible strength with Jackman's maturity.
• Kamen Rider:
  • Kamen Rider OOO: Ankh has been reduced to a disembodied arm at the start of the show, with no knowledge of what happened to the rest of his body. The body is eventually revealed to have come back to life without his mind in it and developed its own childlike personality, referred to in external material as Lost Ankh. Both attempt to consume each other once they meet, with Lost Ankh proving the stronger and eventually winning out after several skirmishes. Eiji's eventually able to kill Lost Ankh, and the original Ankh resurrects from his remains.
  • Kamen Rider Build: Some demonic possesion shenanigans late into the story cause the original identity of Takumi Katsuragi to resurface and replace the person he was for the past year and half without knowing about anything that happened through that time. After a short period, he deliberately returns to the other personality after realizing he was a better person that way.
  • Kamen Rider Revice: After a brief split into separate bodies so they can fight it out, Daiji manages to kill his evil half Kagero and become the sole personality. Unfortunately, this is a much worse solution compared to his brother and sister, who make alliances with their own inner demons: killing Kagero means that Daiji has effectively lobotomized himself, and he becomes an increasingly unstable Knight Templar.
• Although better remembered as the first of the Sweeps Week Lesbian Kiss episodes, L.A. Law episode "He's a crowd" features a man named Gregory Edmondson on trial for murdering his girlfriend, who wanted to break up. His lawyer initially tries to pin it on a violent alter called Sean (Gregory himself thinks it must have been Sean) but upon being provoked a hitherto unknown person called Camille Green emerges. She is Gregory and Sean's aunt. She raised them, and sees herself as their sole protector. She confesses to murdering the girlfriend for causing them pain (and also Gregory's molesting father years earlier — it had been believed a suicide) before putting Gregory and Sean "to sleep" in an effort to keep them out of prison, and becoming the dominant personality.
• Implied to have happened at the end of a Married... with Children episode in which Bud's "cool" personality took over. It had absolutely no visible impact on future episodes (though perhaps that's the joke; Bud's so uncool that even his cool side is uncool).
• The third season of Star Trek: Picard introduces a new Soong-type android/golem whose mind contains the personalities of both Data and Lore. Its creator had hoped to merge the personalities but could not get them to harmonize and so he created a partition between the two minds. Desperate circumstances force the crew to remove the partition in the hopes that Data will emerge with complete control. Unfortunately, Data knows that he has no chance to overpower his brother and Lore ultimately takes over — but because he seized Data's memories, he effectively becomes Data. Slightly spills into Split-Personality Merge as some aspects of Lore's personality (though not the evil ones) are assimilated into the re-emerged Data.
• Stargate-verse:
  • An episode of Stargate SG-1 has Daniel controlled by several different personalities that get in his head.
  • Stargate Atlantis has an episode where Rodney and a (female) Marine wind up sharing his body. They each fight over control of the body, until it can't take their fighting anymore: if one of them doesn't give up and willingly disappear, both will die.
• This is extremely common on Supernatural, due to the prevalence of demonic possessions and sympathetic monsters who want to retain their humanity but are incapable of controlling their predatory instincts. Memorable non-possession examples include Lenore and God-mode Castiel, after he ingests the Leviathan. Throw in manly tears, and you could almost turn this into a drinking game.
• In the Tales from the Crypt episode "Operation Friendship", a lonely man's only companion is his own split personality. When the man starts dating a therapist, said split personality is afraid that she will destroy him and tries to goad the man into killing her. When the guy refuses, his other half decides to "kill" him and take over his life. In the end, the more assertive personality has cowed his former boss and is on the fast track to becoming an executive and is married to the therapist.
• In Terminator: The Sarah Connor Chronicles, Cameron experienced a case of this when her processors glitched due to combat damage, and Cameron slipped into an alternate personality mode that thought it was a woman named Allison Young, who was a resistance fighter in the future who was connected to the future John Connor, whom Cameron interrogated, mimicked the appearance and personality of, and subsequently killed.
• A positive example occurs in The Twilight Zone (1959). In the episode "Nervous Man in a Four Dollar Room", a small-time thug is ordered to kill someone for the first time in his life. His long-buried conscience, manifesting as his reflection given a life of its own, refuses to go along with committing murder and takes over as the dominant personality.
• United States of Tara: Alice, the "housewife" personality, reveals that she's jockeying to be the emergent personality if Tara ever resumes therapy. This was followed by Bryce, Tara's alter based on her childhood abuser, revealing that he wants to "kill" Tara.
• Warehouse 13: "The Ones You Love" reveals that the "Brother Adrian" that Artie's been dealing with all season is a hallucinatory manifestation of an increasingly powerful Enemy Within. Just as Artie realizes this, it grows powerful enough to assume control completely.
• Born vampires from Young Dracula all go through an attempt at this when get their full vampire status. How strong-willed they are seems to determine how much of their original personality is left afterward.

Music

• "My Name is Allen" by Stone Sour.
  There's only room in here for one / And I've decided it's not you
  I had to do what must be done / You would have done it too
• This happens to the protagonist of Nine Inch Nails's The Downward Spiral between the songs "The Becoming" and "I Do Not Want This", during which "the Machine" takes over his mind, culminating in him going on a rampage in "Big Man with a Gun".
  The me that you know, he doesn't come around much
  That part of me isn't here anymore

  — "The Becoming"

Music Videos

• The video for Foo Fighters' "Breakout" has a meek Dave Grohl becoming the rock star Dave Grohl after losing both his medication and his shit (inspired by Me, Myself & Irene, on which the song was included).

Theatre

• In Noah Smith's stage version of The Strange Case of Dr. Jekyll and Mr. Hyde, Hyde stages one in the final scene, planning to inject himself one more time to stay in control permanently, as Jekyll feared that's what would happen if he did.

Toys

• BIONICLE: Inverted. In one of the alternate universes Takanuva stumbles through, the alternate Makuta Teridax absorbs Matoro, who failed in his mission to save Mata Nui in this universe. When Makuta absorb other beings, they normally absorb their bodies and minds, but Matoro fights back, killing himself and Teridax, becoming the hero he was destined to be.

Professional Wrestling

• Along with wrestling as himself, Mick Foley also wrestled under the personas known as "The Three Faces of Foley", consisting of Cactus Jack, Mankind, and Dude Love. No one ever knew when he switches personas, resulting in one hell of a Wham Episode when he let Cactus Jack take over to fight Triple H in 2000.
• Black Serpent and Timothy Krane got to Bill Black in Fringe Pro Wrestling and manipulated him into suppressing his split personality Will White.
• After numerous months languishing in absence and bad booking, Bray Wyatt returned to TV as a Depraved Kids' Show Host version of himself - cardigan and all - hosting the Firefly Fun House. As each episode progressed, it became clear that this version of Wyatt was even more unhinged than his "Eater Of Worlds" persona until, finally, he debuted his new gimmick; a silent, demonic facet of Bray's personality known only as "The Fiend".

Tabletop Games

• The Harrowed from Deadlands are constantly in danger of this, since they owe their very existence to the demons possessing them. Except Stone. He's already such an evil, cruel, monstrous asshole that his Manitou just hides in the back of his head and tries not to call attention to itself.
• What happens to Experiments in Bleak World if they get too inhumane for the voices to stomach or are a little too liberal with their magic.

Video Games

• In Twisted Metal: Head-On, Marcus Kane gives into Needles Kane, aka Sweet Tooth. Interestingly, however, it's not a complete takeover, but rather they seem to be working together, thereby making Dark Tooth and Tower Tooth (the two cars they drive together) the strongest in the game.
  • Played straight in the 2012 game, where the Sweet Tooth persona eventually took over the Marcus Kane one after years of trying to drive him insane.
• The bad ending of Soul Nomad & the World Eaters involve this, with Gig using your greed to destroy the main character's soul and taking over his/her body. The 'bad' ending of the Demon Path reverses the roles, with the main character destroying Gig instead.
• Both the good and the evil ending of The Suffering: Ties That Bind results in either Torque or Blackmore wiping the other personality out completely.
• The bad ending of Manhunt 2- achieved by killing people as gruesomely as you can - has Leo killing off Daniel's personality and becoming the sole resident of his body.
• Near the end of Planescape: Torment you get trapped in a place where you encounter three of your previous "incarnations". The Practical Incarnation wants to do this to you because he can't accept that he lost and got killed despite his ruthlessness. You can't convince him out on it, but you can turn his attempt back on him to absorb him. The Paranoid Incarnation thinks you're a bodysnatcher/impostor and wants to destroy you. He'll submit to a Split-Personality Merge if you can convince him otherwise. If you can't manage that, you'll have to kill them and lose the XP you could get from merging with them. The final you, the Good Incarnation, has no desire to do anything like this and willingly merges with you without making you fight for it.
• Vampire: The Masquerade - Bloodlines has a scene where, after being led along by the two, you finally confront Jeanette and Therese Voermann — wait, make that Tourette Voermann. One half of her face is done up in Therese's professional businesswoman style, while the other half is done up in Jeanette's slutty schoolgirl style, and the two sides speak in turns about wanting to kill the other. Depending on the dialogue you choose, either Jeanette kills Therese, Therese kills Jeanette, or the two personalities decide to put aside their differences and coexist.
• Done very strangely in the Warcraft series; Arthas was a paladin who is corrupted by the Lich King, becomes his champion, then later merges with him, but then Arthas takes over the Lich King, an entity of godlike mental power. A dark lord taken over by another dark lord who is later revealed to be slightly less evil than everyone thought him to be when they became one dark lord.
• One of the main plot points of Riku's story in Kingdom Hearts: Chain of Memories and its remake is that Riku is fighting off the last of Ansem's darkness within his Heart. Several times he almost falls to it, and once he actually does; however, how it happens depends on the version. In the original, after completely dominating Lexaeus in their fight, the latter blows himself up in an attempt to drag the latter down into the Darkness. However, in the nick of time, he is able to resist. In the remake, after a stalemate battle, Riku lunges at Lexaeus to finish him off, only to be backhanded into the ceiling and passing out. Unconscious Riku's body is possessed by Ansem who then kills Lexaeus in one hit before Mickey appears and frees Riku.
• Inazuma Eleven: Fubuki Shiro, who is taken over by Atsuya, his inner mind's high ego little brother.
• A positive example can be found in Deadly Premonition, where upon being traumatized and locked in the White Room by Forrest Kaysen, Francis Zach Morgan develops the personality of Francis York Morgan, who takes dominant control in order to protect Zach. At the endgame, Zach is given back control for the final confrontation with Kaysen.
• In Mortal Kombat 9 a positive example appears in Ermac's Arcade Ladder ending. The soul of King Jerrod, Kitana's father and Sindel's husband, eventually becomes dominant in Ermac and becomes Edenia's protector again.
• Super Robot Wars Alpha 3: Subverted When Cobray Gordon was formed from the fusion of Ayin and Ingram, Ingram tries to take over Ayin's body but ultimately realizes that he himself is being absorbed by Ayin
• In The Elder Scrolls series, Sheogorath, the Daedric Prince of Madness, is a split personality of Jyggalag, the Daedric Prince of Order. When the other Daedric Princes grew afraid of how powerful Jyggalag was becoming, they used their powers to curse him into becoming the very thing he hated the most. Once every Era, Jyggalag is allowed to retake control and destroy Sheogorath's (formerly his own) realm, the Shivering Isles, in an event known as The Greymarch. Once the destruction is complete, Sheogorath retakes control and must rebuild in a Vicious Cycle. The events of the Shivering Isles expansion for Oblivion end with you splitting them into two separate and distinct beings by taking on the mantle of Sheogorath yourself.
• In Fallout: New Vegas, Lily's aggressive alternate personality, Leo, who usually appears to her as a completely separate entity standing beside her, will take over her body when she goes down to 1/4 of her HP, making her unresponsive to any command. Witnessing this triggers her companion quest where you discover that she's only been taking half-dosages of her meds. You can convince her to keep doing what she's doing, take the full dosage to suppress Leo completely at the cost of making her weaker in combat, or stop taking them altogether, which causes Leo to come out at 1/2 HP but makes her much stronger in combat. Similarly, Dog/God in Dead Money may have one of his personalities destroy the other, or merge the two. This is due to them being "Nightkin", a breed of Super Mutant whose overuse of Stealth Boy cloaking devices (which Nightkin find highly addictive) have caused them all to develop schizophrenia.
  • Lily and Leo's story, like all companion stories, doesn't have much of a happy ending. For starters, the reason she takes half-doses of her meds is because taking the full dose causes her memories of her life pre-mutation, particularly those of her grandchildren, to become fuzzy. If Lilly stops taking her meds all together, she keeps the memories of her grandchildren... until Leo eventually takes over completely and the once sweet grandma becomes nothing more than a rampaging beast. If she takes her full medication, Leo is silenced for good... but Lily forgets about her past life and throws away the holotape of her grandchildren because it now means nothing to her. If she keeps talking half-dosages, her mind becomes increasingly muddled to the point that she thinks her grandchildren are still alive, and goes off on a futile search for them.
  • Dog and God are in a similar boat. If Dog survives he becomes hunger embodied and devours entire towns by himself. If God survives he patches up the wounds Dog inflicted on their body to silence his nagging (Except for the name "DOG" carved into their chest) and goes west into the New California Republic to find others like him, speaking of the Courier who saved him. If they're merged, the new unnamed personality has no memories and goes on to have a life of his own, praying for the Courier's safety when he hears of the Battle of the Divide.
• In Counterfeit Monkey, this doesn't happen all the way but there are still Fridge Horror implications of it after Alex and Andra (who started out as separate people, but voluntarily fused together as one person to make escaping the authorities easier) are forced to decide whether to betray Alex's father or Andra's boyfriend. Immediately after they make their decision, the personality who got the upper hand in the decision suffers a brief bout of dizziness and from then on becomes the semi-dominant personality. It's done subtly enough that the player might not notice until the very end of the game (when it's revealed that they no longer have equal control of their body and hence cannot be separated), but examining the PC at any point afterwards will reveal that either Alex or Andra feel as if their body has become more the other personality's than their own and that they're more of a hanger-on than a co-partner now, and there's also a subtle increase in pronoun usage for the dominant personality (a greater number of "I"s from Alex, or a greater number of "you"s from Andra).
• In Granblue Fantasy, this happens between Ayer (the original) and his split personality Bowman. Bowman takes over Ayer's body at the end of his Fate Episode, forcing the crew to beat Ayer back in charge.
• American McGee's Alice: Alice's Battle in the Center of the Mind with The Red Queen would have determined which of her personalities would be dominant and which would be cast down and forgotten.
• In Mystery Trackers: The Void Marius Void's criminally-inclined "brother" Sirius takes over his body after killing his psychiatrist, who'd been supplying drugs to suppress the transformation.
• Krieg the Psycho in Borderlands 2 was once a mercenary or Vault Hunter of some sort, until he was captured and experimented on, turning him into a word-salad-spouting Ax-Crazy Psycho like the hundreds of others you gun down during the game. However, his original personality still exists as a voice in his head, and threatens to take over just long enough to commit suicide should the Psycho ever hurt an innocent person.
• The bad endings of both Castlevania: Aria of Sorrow and Castlevania: Dawn of Sorrow involve Dracula seizing control over Soma's body.
• This forms part of the basis for the main plot of Cyberpunk 2077. The main character, V, is hired to steal a chip that contains the digitized personality of rockerboy terrorist Johnny Silverhand, who died 50 years prior to the game's beginning. After circumstances force V to install the chip in their own head, they are then shot in the head, and the chip saves their life by repairing the damage. Unfortunately, it also begins the process of overwriting V's brain with Silverhand's personality, a process which will ultimately result in Silverhand becoming the dominant personality in V's head. The rest of the game is spent trying to discover a way to prevent this. One of the game's endings has V willingly relinquish control of their body to Silverhand, giving him a second chance at life.
• OMORI's Final Boss fight is a Battle in the Center of the Mind between Sunny, a guilt-ridden, depressed young boy and Omori, the personification of Sunny's death wish. In the Bad Ending, Omori takes control and causes Sunny to throw himself off a hospital rooftop. In the Good Ending, Sunny takes control and comes clean about his Accidental Murder to his friend group.
• The second game in the Surface series, The Noise She Could Not Make has this as it's main conflict. A teenage girl is revealed to have a darker, more aggressive personality named Noise who has started to take over due to being forced to live with her abusive uncle.
• A positive example occurs with Veyle in Fire Emblem Engage. Veyle has two personalities: Her normal personality is a kind and friendly person, but she has an evil personality caused by Sombron's mind control channeled through a crown, which enjoys killing and despises humanity, acting as The Dragon to Sombron. Eventually Veyle, spurred on by the words of her sibling Alear, rips the mind control crown off, shattering it and leaving the evil personality unable to manifest any more, which the evil Veyle themselves considers equivalent to death.

Visual Novels

• This is the major twist in the freeware Visual Novel Ori, Ochi, Onoe. The protagonist used to be in love with the sweet and gentle Ori, but Ori turned out to be a split personality of the more violent and temperamental Ochi with the two personalities referring to each other as "sisters" and leading separate lives. Unfortunately, a later eye operation destroyed the Ori personality and left just the Ochi personality who the protagonist subsequently entered a very complicated and twisted relationship with. One of the game's endings has Ori regain control after the protagonist makes it clear that he loves only her, and another ending has the two personalities merge to create a more complete Ochi.
• In Cinderella Phenomenon, Varg was created by Mythos as a darker split personality of Lucette's knight Fritz that would gradually take over Fritz. Varg can initially come out only at night and can be banished by Lucette uttering the trust word Fritz told her, but later on he can come out during the day and Lucette can no longer easily call Fritz back. Fortunately for Fritz, however, his feelings for Lucette rubbed off on Varg and Varg ultimately erases himself so that Lucette can have Fritz back... provided you made the right choices for Fritz's good ending, that is.
• Danganronpa Another: In Chapter 6, protagonist Yuki Maeda is revealed to be a Split Personality of Utsuro, the mastermind of the Killing Game. In the bad ending, Yuki "kills" Utsuro, only to be killed shortly afterwards by Monokuma. In the good ending, Utsuro "kills" Yuki, then lets himself die once he is defeated.
• In Umineko: When They Cry, the young Maria Ushiromiya always tries to convince herself that every time her mother Rosa starts to get very violently angry with her it's because a Black Witch possesses her and takes her place. Maria does this to avoid accepting that her mother, whom she sees as lovingly kind and altruistic, may actually be very abusive and even negligent towards Maria by her own nature.

Web Animation

• A curious example in Red vs. Blue: Reconstruction - when an AI is implanted in a character, the effect is described as being "of the same mind", where the two entities share thoughts. Though the host is usually able to maintain their identity (even if free will is lost), Agent Maine (better known as the Meta) degenerated into a mindless husk after playing host to 7 different AIs at once and stayed that way even when the AIs were removed. Of particular note is the fact that all 7 AIs were Literal Split Personalities of another AI, the Alpha.
• In 50% OFF, Haru has a whole collective of Harus inside his head who talk, argue, or play chess ("Haru, this is checkers") with each other. In Episode 8 the Impulsive Haru somehow shoots another Haru and takes direct control of the brain so he can go swimming, with the consequence that he shot the only Haru who knows how to read. Then in Episode 18, the Haru Who Can Read makes his triumphant return to get Haru back on track after a loss. The first step of which involves slaughtering a bunch of other Harus and building statues to himself in Haru's mind.

Web Comics

• Dean & Nala + Vinny: One of the comic's ongoing plot lines is the transformation of Nala, a regular cat into the savage Jungle Cat Nala. This transformation is triggered by the sight of certain birds and other outdoor animals. The lettering and shape of her thought balloons and her outline become a lot more jagged. She also gets the Black Eyes of Crazy and a Slasher Smile, and she refers to her friend Vinny (a roach) as "bug child".
• Homestuck: Calliope, a sweet and genuinely kind girl, shares a body with Caliborn, a barely restrained sociopath. At the end of Act 6 Act 3, Caliborn becomes not so restrained, escapes from his confines, and starts a session on his own, taking over their body completely and burying Calliope in the process. However, some characters believe that she may not be entirely dead and that in fact finding her might be the key to defeating Lord English once and for all. The author mocks Caliborn for doing this, since he stunted his own Character Development by averting the Split-Personality Merge that Cherubs normally go through.
• In Mob Psycho 100, the main character, Mob, has one of these that takes over in times of great emotional pain.
• In The Order of the Stick Durkon does this to the evil vampiric version of himself. Specifically, he tricks the vampire into absorbing all of Durkon's lifetime of experiences that went into making him who he is. Since the vampire has had no equivalent lifetime of experiences himself, this turns him into a duplicate of Durkon himself. This is an unusual case, as Durkon was definitely the "weaker" personality in terms of power; in fact he had no control over the body at all.
  Durkon: But...ye know wha ye are if'n ye haf me body an' all me joys and sorrows?
  Both personalities together: Yer me.

Web Original

• Whateley Universe: Sara Waite is really a Great Old One who is supposed to evolve into The Kellith, a being who will wipe the earth of humanity and re-populate it with her spawn. She ends up having a fight to the death with The Kellith in a Journey to the Center of the Mind.
• Twig: Late in the story Sylvester completely shuts down emotionally, entering into a Heroic Safe Mode where his hallucinations of the friends he's left behind take control. This eventually culminates in the Evette persona, a manifestation of his pain and need to lash out, taking full control. She sets Sy on a self-destructive course between rebels and the local nobility, intending on a quadruple cross but in the end desiring to hurt as many people as possible before they finally go down, and Sy's friends are barely able to rescue him.

Web Videos

• One possible interpretation of the ending of Dr. Horrible's Sing-Along Blog speculates that in the wake of Penny's death, Billy was consumed by the Dr. Horrible persona. If so, it would add a new layer of subtext to why during the end credits, Penny's peaceful melody gets swiftly drowned out after a few seconds by Dr. Horrible's march.
• Done in a masterfully nightmarish way in Marble Hornets. In Entry #61, we're treated to a video of the hooded masked man stealing Tim's medication while Tim is in the bathroom during a coughing fit. After Hoody hides, Tim stumbles into the room and undergoes a disturbingly realistic seizure, then jerkily climbs to his feet and absconds, all with the heavy implication that his other personality, the original masked man, is back in the driver's seat. Amongst the evidence that Masky is in control is his pronounced limp- after his leg was previously broken, he'd been limping up to his last chronological appearance in the series.

Western Animation

• Norman Osborn undergoes this in Spider-Man: The Animated Series.
  Green Goblin: (to Harry Osborn) Your whining simp of a father doesn't exist anymore. I am the ultimate evolution of Norman Osborn!
• X-Men: Evolution, episode "Sins of the Son". Charles Xavier discovers he has a son in Scotland, David Haller, and goes to meet him, only for two other boys to enter the fray as well. These three boys (David, Ian, and the evil Lucas) are all parts of the same being. Xavier tries to help expunge Lucas, but ends up locking away David, forever losing his son as Lucas goes off, never to be seen again (as the series was cancelled before this story could continue).
• In South Park, at the end of "City Sushi", the police allow Dr. Janus to keep on thinking he's Lu Kim, since Lu Kim owns the only Asian restaurant in town after City Sushi was destroyed.
• In Total Drama All-Stars Mike was in the previous season was established as having several different personalities. In the episode "Evil Dread" the previously unknown personality Mal is set free when Mike is hit in the head with a shovel, albeit slightly, as he switches in and out at random. Some episodes later Mike attempts to seal him away again by hitting his head on a large rock, but it only serves to imprison Mike in his own mind and give Mal free reign.
• In the Ben 10: Omniverse episode "Max's Monster", Max's Evil Former Friend Phil comes back after a long stint in the Negative Zone mutated and insane after he was used as a test subject for the Nemetrix. He frequently transforms into a savage energy-eating monster with a mind of its own and begs the heroes to help him. Ben is suspicious but Max and Rook are willing to try. Ben is Properly Paranoid, since "Phil" soon admits that "there hasn't been a Phil in this body for years". The monster personality has been in full control the entire time, and Phil's original personality is long gone.
• In The Amazing World of Gumball episode "The Name", when Gumball's discovery of his first name being Zach results in "Zach" becoming his own person, the latter tries to alter the former's memories to erase him from existence.
• Adventure Time has this happen to Simon Petrikov, as documented by his tapes. Although the moment in which he fully became the Ice King has yet to be shown onscreen, the tapes show him increasingly slipping in and out of his current persona's mannerisms; while the later episode "Simon and Marcy" shows him initially resisting this, but the end of the episode makes it clear that he's losing himself and that this trope will soon occur.
• The Avengers: Earth's Mightiest Heroes has a rare consensual example — Bruce Banner lets the Hulk take over his body as long as the Hulk works alongside the Avengers as a hero. Eventually, Bruce is allowed to have control for one day a month.
• Kaeloo: The episode "Let's Play Grown-Ups" suggested that later in Kaeloo's life, her alternate form, Bad Kaeloo, would take over.
• In the series climax of OK K.O.! Let's Be Heroes, this happens to two different people:
  • While K.O. and T.K.O. acted as a team for a while, the former eventually locked the latter in his subconscious once his behavior got out of control. T.K.O. returns the favor as soon as he gets the chance when K.O.'s resolve is weakened, trapping him instead and resulting in this. It's only resolved when K.O. finally accepts that T.K.O. is a natural part of him that's always been there, and they undergo a permanent, much more benevolent Split-Personality Merge instead.
  • "Shadowy Venomous" claims that he's a merge between Shadowy Figure and Professor Venomous, but several factors^note namely, the fact that he looks almost exactly the same as Shadowy Figure, refers to Venomous in the third person but never does so with Shadowy, and his Boss Subtitles ("Venomous is GONE NOW" "Shadowy Figure has overtaken Venomous")heavily imply that he's really a result of Shadowy doing this to Venomous. T.K.O. eventually resolves this by beating Shadowy Figure out of Venomous and destroying him for good.
• The Simpsons: The "Treehouse Of Horror XXXIV" segment "Ei8ht" is set in an Alternate Continuity in which Sideshow Bob successfully murdered Bart in "Cape Feare". While the adult Lisa, now a criminal psychologist, assumed she overcame the trauma of watching Bart die, she developed a second murderous personality that murdered many firstborn Springfielders. She eventually gets total control after Lisa is arrested, considering the original personality another of her victims. To Sideshow Bob however, he complains about how cliche the Split Personality trope is, which doubles as a Fourth Wall break.
  Sideshow Bob: Trope alert! Call the first thought police!

Real Life

• An episode of the dramatized court-case anthology series The Judge dealt with a female dissociative identity disorder patient who, in the episode's surprise twist, turned out to be the victim of her psychiatrist, who was having an affair with her Femme Fatale persona and plotting to destroy her original personality so the two of them could be together. While the script might've involved some dramatic exaggeration ^note there have been numerous cases of unscrupulous psychiatrists exploiting clients who either really are multiple or have been led to believe they are, there are real-life cases of people in MPD / DID groups plotting — or at least wishing — to kill their primary selves physically, without recognizing that if they're successful, they'll die too.

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