Split Personality Merge

Jekyll and Hyde, BBFFs?]]

""You know, Nana! We're gonna live together from here on out!!""

- Yaya, Othello

So Bob is also Charlie, maybe even with a little Albert hiding in there somewhere. There are many possible reasons for the existence of these split personalities, but this co-habitation is rarely peaceful or long lasting. It usually results in a Battle in The Center of The Mind to try and find out which personality will take over. Sometimes though, the winner might not reduce the loser to a tiny, powerless voice or destroy it completely, and instead offers to become one again. With a little Epiphany Therapy, Applied Phlebotinum or even actual psychotherapy, they merge into a single, whole person that is greater than the sum of its minds.

The resulting merged personality is usually a composite of the parts that is well and truly psychologically stable, this is especially true if they were an id, ego, and super ego. If they were moral or temperamental opposites, the resulting merged personality will keep traits of both. This merger includes combat ability and powers, so if the character had a moron and a badass coexisting, the united whole will be a Badass all the time... while occasionally tripping on banana peels. Similarly, if the reason for the personality split was to seal awesome cosmic powers away (resulting in a Super Powered Evil Side; see both Enemy Within and Enemy Without) the united self will have full control over these powers without risk of Superpower Meltdown or corruption.

Truth in Television, what with being one of the recommended treatments for actual Split Personality Disorder.

Anime & Manga

 * Piccolo and Kami of Dragonball Z, who had become a Literal Split Personality decades earlier. (With a little Reincarnation in between. It's complicated.) Not to be confused with the time Piccolo fused with Nail, a completely different and unrelated (though identical-looking) Namekian.
 * In Gundam 00, Allelujah Haptism temporarily merges with his violent Split Personality Hallelujah Baptism to becomes "the Super Soldier" with the piloting skills of two men, or as fans call him, "Doublelujah". This is visually demonstrated by the fact that Allelujah always has his right eye covered by his hair, while when Hallelujah takes over, he sweeps the hair over to cover his left eye instead. When both personalities work together, both eyes are exposed.
 * Similar situation with Une in an earlier Gundam series, Gundam Wing. Une has two personalities, "Lady", a cold-hearted and ruthless military commander and "Saint", who is kind and gentle but ineffectual. At the end of the series, a new personality emerges which has Lady's strength of character and Saint's niceness.
 * Houshin Engi has this with Taikoubou and . They later  . Although.
 * Change 123 is all about trying to merge the personalities of Motoko and HiFuMi.
 * Happens at the end of the Mahoraba manga.
 * Happens to Yaya in the end of Othello.
 * Often overlooked, in Yu-Gi-Oh, Yugi and the pharaoh usually combine their minds when dueling. The reason this is overlooked is because Yugi merged with the pharaoh looks pretty much exactly like the pharaoh all by himself. On account of the pharaoh looking like an older version of Yugi.
 * In Yu-Gi-Oh GX, this occurs during his final duel against Yubel when Juudai accepts that he is Haou, the Supreme King, and no longer fears or denies that power.
 * In Bleach, Ichigo's power manifested in the forms of Zangetsu, his Zanpakuto, and his Inner Hollow. In time,.
 * In Magical Project S, Misao becomes a lot stronger mentally when she accepts her Pixy Misa Dark Magical Girl persona. (And has full control when turning into Pixy Misa later.)
 * Hikaru and Nova in Magic Knight Rayearth, when Hikaru comes to realize.

Comicbooks

 * Doc Samson once pretended to have done this to the Hulk and Bruce Banner, via Epiphany Therapy. But eventually the change in premise became too much of a problem for the Hulk's title, and the writers made use of the fact that Therapy Does Not Work That Way to establish that Samson had really just created a new, if more stable, alternate. Tossing out the fact that Doc Samson wasn't really in control of the process and didn't fully understand what was happening at the time.
 * Professor X's wayward son Legion had his personalities integrated... into one guy who was far worse than his previous selves put together. The result was the Age of Apocalypse.
 * The Green Goblin has undergone this after his 1996 comeback, the Goblin previously veering between being an outright Split Personality of Norman Osborn, a psychotic break from reality and the power fantasy of an unstable Corrupt Corporate Executive who just won the Superpower Lottery. Naturally, the amalgation of a mentally ill white collar criminal with his homicidal maniac alternate persona did not exactly make things better- the new Norman Osborn was a Magnificent Bastard Complete Monster who developed particularly twisted views on his emnity with Spider Man and graduated from millionare industrialist to head of SHIELD (because Humans Are Morons). Recently, the Goblin has shown signs of making a comeback, in the form of delusions and homicidal mania.
 * Deaths Head II gained independence after the Minion cyborg assimilated the minds of 105 of the most deadly minds in the universe, only to have its last target (the original Deaths Head) take over its programming and form a gestalt personality.

Fan Fiction

 * The Doctor Who comic The 10 Doctors demonstrates a rare version of the trope. As the title suggests, the Doctor's regenerations 1 through 10 all band together to save the universe.  In order to defeat the programming there is a Battle in The Center of The Mind where the Doctors all form one persona- an amalgam of his multiple personalities.
 * Occurs to Twilight Sparkle near the latter end of Ponies Make War. Earlier in the story, the psychological trauma of being transformed into Nihilus had caused her mind to split in two -- the dominant, peaceful-to-a-fault Sparkle, and the more brutish Twilight. The two personalities spend quite some time arguing, with Twilight pushing for a merge to restore themself to a full and equal mind, but Sparkle being too afraid that Twilight will pull a Split Personality Takeover and be as monstrous as Nihilus was. Eventually, . Cue asskicking.
 * Pops up in Pinkie Pie's reharmonizing chapter in the Pony POV Series:

Film

 * The author and his cartoon character are merged in Monkeybone.
 * "I'm calling the shots from now on, Hank. I don't need you to fight my battles for me. If you can back down from something this important, you're nothing at all. YOU'RE NOTHING AT ALLLLLLLLLLLLLL!"
 * "That's my secret, Captain. I'm always angry."

Literature

 * This happens to the main character at the end of City of Illusions by Ursula Le Guin.
 * Dandra and Tetkashtai in the Dragon Below trilogy merged into one person at the end of the second book, combining Tetkashtai's psionic power and academic knowledge with Dandra's stubbornness and mental stability to form one psion much more powerful than the sum of her parts.
 * Susannah Dean in The Dark Tower. She originally alternated between the personalities of Detta Walker (kind of psycho and seriously badass) and Odetta Holmes (a wonderful person, but often completely useless). Forcing them to notice each other led to them merging into Susannah, who keeps Detta's ferocity and Odetta's kindliness and feelings for Eddie. Still, the merge isn't perfect; at one point, Susannah has to let Detta take over again because she learned a lesson Odetta never did.
 * Rand Al'Thor suffered a long time clashing ever more obviously with the voice in his head (which could take over his body at times), that of his previous incarnation, Lews Therin Telamon, and finally snapped in a long overdo psychotic break. Eventually he.
 * Happens to Tahiri Veila and her implanted Vong personality, Riina Kwaad, in Force Heretic 3: Rebirth. Riina, being a Proud Warrior Race Girl, had attempted a Split Personality Takeover, but settled on the compromise when she realized that "killing" Tahiri would be disastrous for both of them.
 * Robert Sheckley has a story where a man underwent a treatment in his childhood by having his extra personalities siphoned away into artificial bodies. The story is about him searching for them all over the Solar System..
 * The Animorphs starfish book ended with an Erek-mediated merging of the two halves.

Live-Action TV

 * In the Buffy episode The Replacement, Xander's personality is magically split into two bodies - one being confident, competent Xander and the other being awkward, pathetic Xander - and then merged again at the end.
 * In the season 6 finale of Supernatural, Sam is stuck in a Mental World where his identity has split into three personalities: Sam, Soulless Sam, and the Sam who's been tortured in the Cage. Finding his way out of there requires the other two to merge back into him.

Music

 * There's an unusual one at the climax of The Who's Rock Opera Quadrophenia. In "The Rock," as Jimmy's life flashes crawls before his eyes, the musical themes representing aspects of his personality merge into one. Hm? You say I can't possibly get all this information from an instrumental? You're right: It's all there in the manual liner notes.
 * In another Rock Opera example, Green Day's American Idiot has this happening to St. Jimmy, the evil side of Jesus of Suburbia ("Jimmy died today; he blew his brains out into the bay").

Tabletop Games

 * This is a central mechanic of the game, Vox, where characters incorporate the voices in their head as a part of themselves they have 'forgotten,' growing closer to perfection each time.
 * Changeling: The Lost has an Enemy Without variant with regards to the fetch, an impostor made from a fragment of the changeling's soul to fill their place after they're taken by the Gentry. Most changelings are just content to kill their fetch - either in an attempt to reclaim their life or destroy one of "their" tools - but it's possible for a changeling and a fetch to come to a deep, intricate understanding of how each one reflects aspects of the other's personality and being. If that happens, the changeling and fetch merge into one being, with the changeling's Clarity going up a level. Keep in mind this is a long, difficult process, and odds are other changelings won't look on you so kindly for attempting it...

Video Games
"Arthas/Ner'zhul: Now, We are one."
 * Happens with  in Final Fantasy IV the After Years.
 * Kingdom Hearts 2, with Sora and . To make things even messier,   comes into the mix in 358/2 Days.
 * And in Birth By Sleep, it's revealed that.
 * Also in Birth By Sleep,
 * Not quite a merger, but in Vampire: The Masquerade Bloodlines, in the climactic dialog with, with high enough stats you can persuade them to make amends and tolerate each other, in which case they bury the hatchet and peacefully coexist.
 * Fei in Xenogears merges with no less than three (possibly four, though that one was an Empty Shell) alternate personalities after convincing them to. This is remarkable since he wasn't the original, but the third personality.
 * In The Darkness videogame, Jack Estacado manages to control the Darkness, a demon spirit that existed in his family since WWI, not through guns but by absorbing it into his own spirit. This allowed him to control the Darkness, but the Darkness reminded Jackie "with each life you take. I grow closer to owning your soul!" Guess what he has to do next to reach his Uncle Paulie?
 * Even is not enough to escape: Jackie  after  while he's being restrained by, but comes back with the Darkness still possessing him.
 * In the War Craft storyline, the first Lich King, Ner'zhul, has mostly total mental control over all the undead. He chooses his Champion, Arthas, to be the host of his soul which has been trapped in the frozen throne. It could be argued that Arthas's taking of the title of Lich King is one of these.


 * It was later revealed to be a Split Personality Takeover.
 * It's not fully explained, but this happens in the Dimensional Vortexes in the DS re-release of Chrono Trigger.
 * In the Fallout New Vegas DLC Dead Money, with a high enough Speech skill you can do this to God/Dog to help him peacefully.
 * In the normal and good endings of Tales of Symphonia Dawn of the New World,

Webcomics

 * Minmei Wu and Professor Sorgaz in The Wotch, once Minmei is made aware of her status as a gender bent teacher dunked in the Fountain of Youth. Perhaps a slight twist on this trope, Minmei is perfectly willing to go away so Sorgaz can return to his normal life. It is Sorgaz who proposes merger to live out a Second Chance.
 * This is one of the possible explanations for the ending of the Aiden and Brownwyn arc in Misfile. It wasn't made terribly clear, but Rumisiel did force the Wraith-thing to into Bronwyn's psyche and told it to stay there, and Bronwyn did regain her affection for Aiden as a result.
 * Inverted in Homestuck.  begins with the stable merged personality when stoned. Then he sobers up, the personalities splits, and both of the resulting personalities are Ax Crazy.
 * Attempted a few times by Jix and her alternate personalities Remula and Lamerix. The first time it seemed to work for a while, but broke down when she was cloned and Remula was seemingly transferred to the clone . Another time a psychologist tried to get her personalities to destroy each other.
 * Attempted a few times by Jix and her alternate personalities Remula and Lamerix. The first time it seemed to work for a while, but broke down when she was cloned and Remula was seemingly transferred to the clone . Another time a psychologist tried to get her personalities to destroy each other.

Web Originals

 * Happens to  in the Metamor City novel Making The Cut.
 * The goal of the Meta (a gestalt entity of A Is created as Literal Split Personalities) in Red vs. Blue: Reconstruction is to reconstruct the original Alpha AI from which they were split off. According to Word of God, the first AI in the Meta (Sigma) intended to rebuild the Alpha with itself as the leader.