[[quoteright:330:[[Series/{{Jekyll}} http://static.tvtropes.org/pmwiki/pub/images/HydeAndJekyllShakeHands.jpeg]]]]
[[caption-width-right:330:Jekyll and Hyde, [=BFFs?=]]]

->''"You know, Nana! We're gonna live together from here on out!!"''
-->-- '''Yaya''', ''Manga/{{Othello}}''

So Bob is also [[SplitPersonality Charlie]], maybe even with a little [[GhostInTheMachine Albert hiding in there somewhere.]] There are many possible reasons for the existence of these [[SplitPersonality split personalities]], but this co-habitation is rarely peaceful or long lasting. It usually results in a BattleInTheCenterOfTheMind to try and find out which [[SplitPersonalityTakeover personality will take over]]. Sometimes though, the winner might not reduce the loser to a [[NotSoImaginaryFriend tiny, powerless voice]] or [[LossOfIdentity destroy it completely]], and instead offers to become one again. With a little EpiphanyTherapy, AppliedPhlebotinum 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 [[TheMcCoy id]], [[TheKirk ego]], and [[TheSpock super ego]]. If they were [[GoodAngelBadAngel moral]] or [[RedOniBlueOni temperamental]] opposites, the resulting merged personality will keep traits of both. This merger includes combat ability and powers, so if the character had a [[CrouchingMoronHiddenBadass 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 SuperPoweredEvilSide; see both EnemyWithin and EnemyWithout) the united self will have full control over these powers without risk of SuperPowerMeltdown or corruption.

Minus the superpowers, this is the RealLife scenario believed in by doctors working with multiples clear back to [[https://books.google.com/books?id=oDlq6EtyR8wC&dq=%22My+life+as+a+dissociated+personality%22&printsec=frontcover&source=bl&ots=jG6Ha_RbAf&sig=Y_R015UyfFOxrGfDhIjzPb3V9sA&hl=en&ei=bA34SYyBM6b4tAO336nsDg&sa=X&oi=book_result&ct=result&resnum=1#v=onepage&q=%22My%20life%20as%20a%20dissociated%20personality%22&f=false Dr. Morton Prince in the early 1900s]]. Many books on multiple personality disorder follow this storyline. Actual multiples report YMMV on this experience. Some who have gone through it deliberately de-integrated later, feeling that the whole is ''less'' than the sum of the parts. ''Literature/WhenRabbitHowls'' is written by members of a multiple collective who spoke out vehemently against the idea as a form of murder. To them, it's better to learn how to communicate and work together as a SplitPersonalityTeam or MindHive.



[[folder:Anime & Manga]]
* ''Manga/DeathNote'': Light Yagami has a minor variation of this when he regains his memories, making this one of the rare unhealthy villainous examples.
* ''Anime/DragonBallZ'':
** Piccolo and Kami, who had become a LiteralSplitPersonality decades earlier. (With a little {{Reincarnation}} in-between. [[Manga/DragonBall It's complicated.]]) Not to be confused with the time [[FusionDance Piccolo fused with Nail]], a completely different and unrelated ([[IdenticalStranger though identical-looking]]) Namekian.
** The Buu saga liked to play with this. For starters, the FusionDance merges two fighters' personalities as well as their appearances. After that, Buu is absorbed by his [[EnemyWithout dark side]], but the new hybrid form is restrained from killing some people due to his good side's influence... ''[[KillEmAll Some]]'' [[KillEmAll people]].
* ''Franchise/{{Gundam}}''
** In ''Anime/MobileSuitGundam00'', Allelujah Haptism temporarily merges with his violent SplitPersonality Hallelujah Haptism to become "the SuperSoldier" with the piloting skills of two men, or [[FanNickname 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 (and he speaks with both voices and personalities in turn).
** Similar situation with Une in an earlier series, ''Anime/MobileSuitGundamWing''. Lady Une has two personalities, "Iron Une", a cold-hearted and ruthless military commander and "Saint Une", who is kind and gentle but ineffectual. She spending about half the series in a coma and wakes up a couple of episodes before the finale, having resolved the conflict and now combining the military skill with the compassion.
* ''Manga/SoulHunter'' has this with Taikoubou and [[spoiler:Ou Eki]]. They later [[spoiler:merge together to become Fukki]], although [[spoiler:Taikoubou is the main, dominating personality]].
* Zigzagged a bit in the anime ending of ''Manga/{{MAR}}''. [[spoiler: Snow was a clone created from a piece of Koyuki's soul. Making them not so much split personalities so much as original and copy. In the end, Snow merges back into Koyuki to become one whole person to be with Ginta on Earth. The ending seems to indicate a complete merge of both sets of memories, while retaining the same personality. It helps they essentially acted as the same person anyway.]]
* ''Manga/{{Change 123}}'' is all about trying to merge the personalities of Motoko and [=HiFuMi=] [[spoiler:and Zero]].
* Happens at the end of the ''Manga/{{Mahoraba}}'' manga.
* Happens to Yaya in the end of ''Manga/{{Othello}}''.
* Often overlooked in the English dub of ''Anime/YuGiOh'', 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 ''Anime/YuGiOhGX'', this occurs during his final duel against Yubel when Jaden accepts that he is the Supreme King, and no longer fears or denies that power.
* In ''Manga/{{Bleach}}'', Ichigo's power manifested in the forms of Zangetsu, his Zanpakuto, and his Inner Hollow. In time, [[spoiler: he comes to dominate both of them, learning how to use their power for himself. He also tends to take on aspects of their personality and appearance when using their power, such as the coat he acquires in Bankai mode and the mask and personality changes that accompany his Hollowfication. Recently, Zangetsu and the Inner Hollow merged themselves while Tensa Zangetsu was trying to teach Ichigo the [[EleventhHourSuperPower Final Getsuga]]. The result seems to be Tensa Zangetsu wearing a white robe instead of a black one, and having the top part of the Inner Hollow's super evolved mask. However, his personality seems to remain as that of Zangetsu's. Ichigo then merges with THIS personality, and takes on its confidence and... moodiness.]]
* In ''[[Anime/PrettySammy Magical Project S]]'', Misao becomes a lot stronger mentally when she accepts her Pixy Misa DarkMagicalGirl persona. (And has full control when turning into Pixy Misa later.)
* Hikaru and [[EnemyWithout Nova]] in ''Manga/MagicKnightRayearth'', when Hikaru comes to realize [[spoiler: Nova was created from Hikaru's feelings of guilt and regret for killing Princess Emeraude, and finally learns to accept these feelings and forgive herself]].
* ''Manga/RosarioToVampire'': Even after [[spoiler: the destruction of the [[RestrainingBolt rosary]] and her seeming [[DeathOfPersonality demise]], Outer Moka's soul still exists within Inner Moka's body, and by the final chapter, the two have become one, signified by Inner Moka's [[MulticoloredHair silver hair turning pink at the ends]]. This merger overlapped so completely with Inner Moka's own [[DefrostingIceQueen defrosting]] that nobody other than her father (not even newly merged Moka herself) realized it was happening at first]].
* ''Manga/WChange'' both inverts this, then plays it straight. Maki's two personalities used to be one entity -- with the "light" side representing her happiness and joy and the "dark" sight representing her anger and sorrow, but they diverged into two separate beings at some point. Later, the personalities merged back together, allowing Maki to switch between her two sides at whim.
* In ''Anime/ShamanicPrincess'', the heroine, Tiara, confronts her uncontrolled magical powers in the form of a shadowy, seductive EnemyWithout. It gets the better of her at first, but eventually Tiara realizes its power is a result of her fear, so [[ImNotAfraidOfYou she asserts herself]] and [[NeckLift shows it who's boss]]. It merges into Tiara, giving her access to her SuperMode for the first time.
* Done uniquely in ''Anime/DanganRonpa3''. [[spoiler:One of the main characters, Hajime, underwent a surgery that replaced his personality with a different one, which was then renamed Izuru. After [[VisualNovel/SuperDanganRonpa2 the events of the second game]], the two of them managed to reach an accord and merge, signified by heterochromia--one eye Hajime's green, the other Izuru's red. However, rather than one of them being dominant, the resulting persona has traits from them ''both'', and upon being asked which name he goes by in the OVA simply says "either is fine".]]

[[folder:Comic Books]]
* Doc Samson once pretended to have done this to [[ComicBook/TheIncredibleHulk the Hulk and Bruce Banner]], via EpiphanyTherapy. But [[FailureIsTheOnlyOption 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. [[CanonDiscontinuity 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.]]
* ''ComicBook/XMen'': 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 ComicBook/{{Age of Apocalypse}}. Before, each of his selves only had access to one mutant power, and the good and neutral personalities acted as somewhat of a restraint on the evil one. The amalgamated version became an [[TheUnfettered utterly ruthless]] WellIntentionedExtremist with access to ''all'' of Legion's many powers ([[SuperpowerLottery which turned out to be stronger and more varied than anyone realized]]).
** Later, as the focus character of the X-Men: Legacy title, CharacterDevelopment allows him to do this without going off the rails.
* The Green Goblin has undergone this after his 1996 comeback, the Goblin previously veering between being an outright SplitPersonality of ComicBook/{{Norman Osborn}}, a psychotic break from reality and the power fantasy of an unstable CorruptCorporateExecutive who just won the SuperpowerLottery. 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 MagnificentBastard who developed particularly twisted views on his emnity with Franchise/SpiderMan and graduated from millionaire industrialist to head of S.H.I.E.L.D. (because HumansAreMorons). Recently, the Goblin has shown signs of making a comeback, in the form of delusions and homicidal mania.
** And very recently, Osborn was purged of the Goblin formula entirely. While he's been BroughtDownToNormal, he sees the sudden lucidity as an advantage in crushing his enemies, and the "good" Norman that used to appear during his early bouts of amnesia is entirely absent.
* ComicBook/DeathsHead 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 ComicBook/DeathsHead) take over its programming and form a gestalt personality.
* In ''ComicBook/ElfQuest'', Two-Edge's mind was split in two by Winnowill, [[spoiler:his ''mother'']]. He tries to use a troll vs. elf ''war'' to decide what he really is. [[note]]Significantly, the war is won by the elves AND their troll allies.[[/note]] Later, instead of running, Two-Edge allows Leetah to heal his fractured mind. His later appearances show him to still be a bit loopy, but with only one mind running the show.
%%* ''Comicbook/GreenLantern'' has Carol growing more stronger when she accepted the Star Sapphire ring willingly to the point that she regains control of herself in her Star Sapphire form this time.
* ''ComicBook/SupermanReborn'' reveals [[spoiler:the creation of the ''ComicBook/{{New 52}}'' continuity caused Franchise/{{Superman}} to be [[LiteralSplitPersonality separated]] into his pre-''ComicBook/{{Flashpoint}}'' and ''[=N52=]'' selves, explaining why were there two versions of Superman flying around at the end of the ''New 52'', when no other character displayed such problem. At the end of the story, they merge into a single, complete version of Superman.]]
* In the schoolgirl comic book ''Julie's Jungle Cousin'' Sue has two personalities: Jungle Sue, a gender-flipped Franchise/{{Tarzan}} who speaks YouNoTakeCandle, acts on instinct and is capable of daring physical feats; and Stuttering Sue, who speaks grammatical English with a stutter and is a physical klutz. By the end of the comic she has managed to integrate the two into one articulate, athletic personality.

[[folder:Fan Works]]
* Occurs to [[WesternAnimation/MyLittlePonyFriendshipIsMagic Twilight Sparkle]] near the latter end of ''FanFic/TheImmortalGame''. Earlier in the story, the psychological trauma of being transformed into [[SuperpoweredEvilSide Nihilus]] had caused her mind to {{split|Personality}} in two -- the dominant, [[ActualPacifist peaceful-to-a-fault]] Sparkle, and the more brutish Twilight. The two personalities spend quite some time [[TalkingToThemself 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 SplitPersonalityTakeover and be as [[HeWhoFightsMonsters monstrous as Nihilus was]]. Eventually, [[spoiler:[[BigBad Titan]] captures Sparkle and tortures her. The pain and desperation causes Sparkle to accept Twilight and fuse back with her, recreating the ''real'' Twilight Sparkle]]. Cue [[HesBack asskicking]].
* ''Fanfic/PonyPOVSeries''
** Pops up in Pinkie Pie's reharmonizing chapter: [[spoiler:Angry Pie, a SplitPersonality representing Pinkie's anger, attempts a SplitPersonalityTakeover by absorbing Pinkie and her other personalities. In order to defeat her, Pinkie and Pinkamena fuse together, and the resulting being defeats and absorbs Angry, before fusing with the other personalities, restoring Pinkie's mind to its full state for the first time since she got her cutie mark.]]
** Happens again in the [[BadFuture Dark World]] timeline, [[spoiler:but differs from the main universe, in that Twilight has to [[JourneyToTheCenterOfTheMind enter her mind]] and talk her personalities into doing it, and she didn't have split personalities the entire time; she ''forced'' her mind back together and a number of factors resulted in it splitting again, allowing Twilight to help her put it back together ''right''.]]
* Fluttershy and Erica eventually perform this in ''FanFic/BecomingPonies''. As do one half of Twilight and Isaac.
* [[http://www.tthfanfic.org/Story-11037/Mediancat+The+Sum+of+Their+Parts.htm The Sum of Their Parts]] is a fanfic that begins by establishing that Faith (from Series/BuffyTheVampireSlayer) [[http://www.tthfanfic.org/Story-10602/Mediancat+April+10+1997.htm is actually an alternate personality]] for WesternAnimation/{{Daria}} Morgendoffer produced to handle her rage over [[spoiler:her family's brutal murder]]. Eventually she winds up in a fight with [[spoiler:Glorificus who steals the mental energy maintaining their separation]]. Then [[spoiler:Willow pulls the same trick on Glory/Ben]]. [[spoiler:Daria's and Faith's minds work together to become "reason, backed by intuition... more than the sum of her parts," while Glory/Ben become completely paralised by indecision: "less than the sum".]]
* ''FanFic/AShadowOfTheTitans'': According to [[EnemyWithin the Queen]], the longer that Jade spends in Shadowkhan form, the more this process will occur with the two of them, until eventually all that's left will be a being with the Queen's amorality, but with Jade's wit to keep her from being StupidEvil.

[[folder:Films -- Live-Action]]
* The author and his cartoon character are merged in ''Film/{{Monkeybone}}''.
* ''Film/MeMyselfAndIrene'': "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!"
* ''Film/FightClub'': "You met me at a very strange time in my life."
* In ''Film/HellraiserIIIHellOnEarth'', [[spoiler:Pinhead Unbound and Elliot Spencer are merged back into the same being, which turns out to be Pinhead. Joey is given just enough opportunity to stab Pinhead and send him back to the Cenobite dimension.]]

* This happens to the main character at the end of ''Literature/CityOfIllusions'' by Creator/UrsulaKLeGuin.
* 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 ''Franchise/TheDarkTower''. 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. [[spoiler:"Poetry-readin' bitch like her never had the time for a little ''ars mathematica''."]] Detta is also prone to resurfacing on her own occasionally, but when she does she is much less vicious than she was originally.
* ''Literature/TheWheelOfTime'': 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 [[spoiler: becomes insanely homicidal and then nihilistic, raving about destroying all humanity as everything is pointless. He and his previous incarnation (which as he seemed to be able to take over Rand's body and control of Saidin can be seen as a split personality) reach a kind of epiphany and he manages to step back from the brink. Afterwards the narration makes clear he will never again hear the voice of Lews Therin again, likely because he at last accepted the simple truth, 'that they were not two people, and never had been']].
* Happens to Tahiri Veila and her implanted Vong personality, Riina Kwaad, in ''[[Literature/NewJediOrder Force Heretic 3: Rebirth]]''. Riina, being a [[ProudWarriorRaceGuy Proud Warrior Race Girl]], had attempted a SplitPersonalityTakeover, but settled on the compromise when she realized that "killing" Tahiri would be disastrous for both of them.
* Creator/RobertSheckley 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. [[spoiler: In the end, he collects them all, expecting them all to reintegrate into his, only to have all the parts, including himself, merge into a completely different persona]].
* The ''Literature/{{Animorphs}}'' [[StarfishCharacter starfish]] book, where Rachel morphs a starfish and ends up split in half, with both halves demorphing into a separate version of herself, ended with an Erek-mediated merging of the two halves.
%%* In Daniel Keyes' novel ''Literature/TheFifthSally''.

[[folder:Live-Action TV]]
* In the ''Series/BuffyTheVampireSlayer'' 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.
* ''Series/TheSecretWorldOfAlexMack'' has Evil Alex and Good Alex merge after both of them had been separated.
* In the season 6 finale of ''Series/{{Supernatural}}'', Sam is stuck in a MentalWorld where his identity has split into three personalities: original Sam, soulless Sam, and the mentally broken Sam who's been [[FateWorseThanDeath tortured in Lucifer's cage]]. Finding his way out of there requires the other two to merge back into him. Unfortunately, soulless Sam is trying to murder original Sam to keep that from happening, and the broken Sam's memories are so [[GoMadFromTheRevelation traumatic]] that [[spoiler: Sam has to be admitted to a psychiatric hospital in season 7.]]
* Despite providing the picture, ''Series/{{Jekyll}}'' averts this. Even though Jackman and Hyde agree to work together, they retain their individual personalities and [[SuperpoweredEvilSide powers or lack of them]]. Their alliance is simply a case of switching voluntarily depending on which would be most useful at any time, and both of them agreeing to devote their respective talents towards the common goal of saving Jackman's family.

* There's an unusual one at the climax of Music/TheWho's RockOpera ''Music/{{Quadrophenia}}''. In "The Rock," as Jimmy's [[MyLifeFlashedBeforeMyEyes life]] [[strike: 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: [[AllThereInTheManual It's all there in the]] [[strike:manual]] liner notes.
* In another Rock Opera example, Music/GreenDay's ''Music/AmericanIdiot'' has this happening to St. Jimmy, the evil side of Jesus of Suburbia ("Jimmy died today; he blew his brains out into the bay").

[[folder: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.
* ''TabletopGame/ChangelingTheLost'' has an EnemyWithout 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 [[TheFairFolk 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 [[SanityMeter 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...
* With the ubiquity of BrainUploading in ''TabletopGame/EclipsePhase'' it's not uncommon for people to make temporary copies or "forks" of themselves and later reintegrate the two. Unfortunately the longer they remain separate the more likely the chance of integration causing [[SanitySlippage stress]].
** Individuals who are willing to push the boundaries of transhuman science have attempted merging completely different egos together, though this almost always results in insanity.
* The goal of the Multiple Men in ''TabletopGame/BleakWorld''. Unlike most [[GoneHorriblyWrong Experiments]], the Multiple Men would rather live with their personalities than silence them and have various methods of getting along.

[[folder:Video Games]]
* Happens with [[spoiler:Kain]] and [[spoiler:[[EnemyWithout Dark Kain]]]] in ''[[VideoGame/FinalFantasyIVTheAfterYears Final Fantasy IV: The After Years]]''.
** This happens to [[spoiler:Cecil]] as well. It turns out that [[spoiler:the [[CastingAShadow Dark Knight]] aspect of Cecil's personality that he cast away [[VideoGame/FinalFantasyIV seventeen years prior]] in order to accept the powers of a [[ThePaladin Paladin]] comes back to life and becomes Cecil's EnemyWithout, serving as a boss late in the game. Upon defeat, the Dark Knight [[BetaTestBaddie questions his identity]], causing Cecil to apologize for repressing this part of his life for so long and pull a YouAreNotAlone on his darker half. This event is crucial for [[HesBack rousing Cecil out of his]] HeroicBSOD (thus restoring his resolve and in-game stats), although Cecil doesn't regain his Dark Knight abilities (no, ''VideoGame/{{Dissidia|FinalFantasy}}'' doesn't count... probably).]]
* In ''VideoGame/LightningReturnsFinalFantasyXIII'', [[spoiler:Lightning and Lumina merge once Lightning accepts the parts of herself she viewed as "weaknesses", which manifested as Lumina.]]
* ''VideoGame/KingdomHeartsII'', with Sora and [[spoiler:Roxas]]. To make things even messier, [[spoiler:Xion]] comes into the mix in ''[[VideoGame/KingdomHearts358DaysOver2 358/2 Days]]''.
** And in ''[[VideoGame/KingdomHeartsBirthBySleep Birth by Sleep]]'', it's revealed that [[spoiler:Ven also merged his heart with Sora's heart and in fact had been in him throughout almost his entire life and all of the ''Kingdom Hearts'' games long before Roxas and Xion came into being. However it might not be the case here since Sora's really only holding his heart for safe keeping and isn't receiving anything from Ven. However, if what the endings of ''coded'' and ''Birth by Sleep'' seem to be implying are true, the merges are only temporary, and the plot of the upcoming games will most likely focus, in part, on giving Ven, Roxas and Xion their own bodies]].
** Also in ''Birth by Sleep'', [[spoiler:Ventus merged with Vanitas, the [[MadeOfEvil personification of his heart's darkness]]. So Sora's about five different people at the end of ''Kingdom Hearts II''. Yeah, it's kind of a MindScrew.]]
*** That's assuming [[spoiler:Ven didn't outright destroy Vanitas at the end of ''BBS'', which is why he fell into a coma almost immediately after in the first place. Vanitas' brief appearance alongside Young Xehanort in ''3D'' ([[AllThereInTheManual a representation of Ventus' heart within Sora reacting to Xehanort's darkness]]) complicates things.]]
** This is finally brought up in ''[[VideoGame/KingdomHearts3DDreamDropDistance 3D]]'', with [[spoiler:Xemnas]] asking Sora "The bits and bytes that have made up your life so far... can you say for sure that they are not just copies of someone else's?" Not to mention the fact that [[spoiler:Sora himself is questioning the wisdom of the merge, saying that Roxas deserves to be his own person]].
* Not quite a merger, but in ''VideoGame/VampireTheMasqueradeBloodlines'', in the climactic dialog with [[spoiler: Jeanette/Therese]], 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. Speaking with them later on reveals they're still separate entities, but apparently much more aware of each other [[spoiler:and the ensuing character is named 'Tourette' by the game.]]
* Fei in ''VideoGame/{{Xenogears}}'' merges with no less than three (possibly four, though that one was an EmptyShell) alternate personalities after convincing them to. This is remarkable since he wasn't the original, but ''the third'' personality.
* In ''VideoGame/TheDarkness'' 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 [[spoiler:Death]] is not enough to escape: Jackie [[spoiler:commits suicide]] after [[spoiler:Uncle Paulie kills his girlfriend before his eyes]] while he's being restrained by [[spoiler:the Darkness itself]], but comes back with the Darkness still possessing him.
* In the ''VideoGame/{{Warcraft}}'' 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.
--> '''Arthas/Ner'zhul''': "''Now, We are one''."
** It was later revealed to be a {{Split Personality|Takeover}} ''[[SplitPersonalityTakeover Takeover]]''.
* It's not fully explained, but this happens in the Dimensional Vortexes in the DS re-release of ''VideoGame/ChronoTrigger''.
* The ''VideoGame/FalloutNewVegas'' [[DownloadableContent DLC]] ''Dead Money'' has Dog and God, a Nightkin with two personalities: the dumb, friendly, always-loyal, always-hungry [[MeaningfulName Dog]]; and the cold, calculating, intelligent, {{Jerkass}} ControlFreak [[JerkWithAHeartOfGold with a heart of gold]] [[MeaningfulName God]]. Essentially, they are the Id and Superego of one single personality, and eventually you have the option of merging the two personalities into one, or have either Dog or God [[SplitPersonalityTakeover take over completely]]. If you merge the two, Dog and God will finally put aside their differences for a brief moment to say thanks and goodbye to you before merging. The merged personality has no memories at all, but has a vague feeling like you've helped him, even though he doesn't know who the hell you are.
* In the [[MultipleEndings normal and good endings]] of ''VideoGame/TalesOfSymphoniaDawnOfTheNewWorld'', [[spoiler:Ratatosk's personality comes to terms with the part of himself that is Emil and the two accept each other as parts of a whole.]]
* A timid Shiro Fubuki from ''VideoGame/InazumaEleven 2'', merging with his HotBlooded alter-ego by the last two chapters.
* Inverted in ''VideoGame/MassEffect3'' to [[spoiler: the geth, formerly a [[MindHive cooperative mass of programs,]] allowing them to become self-aware individuals, after the recently individualized Legion [[HeroicSacrifice merges himself with the Consensus.]]]]
* [[IAmWhatIAm Accepting one's Shadow self]] in ''VideoGame/{{Persona 4}}'' transforms it into a Persona, which isn't quite merged but does act as a GuardianEntity instead of an EnemyWithout.
* In ''VideoGame/LaPucelle'', [[spoiler:Eclair]] confronts and merges with Dark [[spoiler:Eclair]] who is [[spoiler:her]] desire to be free and normal.

[[folder:Visual Novels]]
* Discussed [[spoiler: and averted]] in ''[[VisualNovel/ShallWeDateNinjaShadow Shall We Date?: Ninja Shadow]]'': [[spoiler: In Kagura's route, Saori hears of a medicine that could potentially help Kagura and his SplitPersonality, Homura, merge back together in peace. She goes through lots of danger to get it, but it turns out to be untested and she almost gets it ''force fed'' to her. After all of this is over, Kagura (and Homura) thank her for her efforts, but [[SplitPersonalityTeam they ultimately decide to co-exist and work together on their issues]].]]

[[folder:Web Animation]]
* The goal of the Meta (a gestalt entity of AIs created as [[LiteralSplitPersonality Literal Split Personalities]]) in ''Machinima/RedVsBlue: Reconstruction'' is to reconstruct the original Alpha [=AI=] from which they were split off. According to WordOfGod, the first [=AI=] in the Meta (Sigma) intended to rebuild the Alpha with itself as the leader.
* In ''WebAnimation/{{RWBY}}'', it's revealed that every incarnation of [[spoiler:the being currently known as Ozpin]] will eventually have their original personality fuse with those of the previous incarnations'. The current incarnation, [[spoiler:Oscar Pine]], still has his own identity separate from the collective [[spoiler:"Ozpin"]] personality, but he's accepted the eventuality that he'll ultimately be absorbed.

[[folder:Web Comics]]
* The ''Series/DoctorWho'' comic ''Webcomic/The10Doctors'' demonstrates a rare version of the trope. As the title suggests, the Doctor's [[TheNthDoctor regenerations 1 through 10]] all band together to save the universe. [[spoiler:At one point, Ten gets captured by the Daleks and is brainwashed into "Dalek Tor"]]. In order to defeat the programming there is a BattleInTheCenterOfTheMind where the Doctors all form one persona -- an amalgam of his multiple personalities.
* In ''Webcomic/{{Drowtales}}'', [[OurFairiesAreDifferent fae]], such as elves, are vulnerable to tainting, meaning that their "souls" have been infected by a demon. Usually, the demon will gradually consume the tainted victim, but it is also possible for the fae to merge their "soul" with the demon, leaving the fae's own personality dominant, making them immune to further DemonicPossession, and sometimes giving them access to special abilities originating from the demon.
* Mingmei Wu and Professor Sorgaz in ''Webcomic/TheWotch'', once Mingmei is made aware of her status as a [[GenderBender gender bent]] teacher dunked in the FountainOfYouth and the origional personality reappears. Perhaps a slight twist on this trope, as well; Mingmei is perfectly willing to go away so Professor Sorgaz can return to his normal life. It is ''Sorgaz'' who proposes merger, claiming she already has a better life than he ever did (He proposes merging the best of both worlds-- her friends, his bank account).
* This is one of the possible explanations for the ending of the Aiden and Brownwyn arc in ''Webcomic/{{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.
* ''Webcomic/{{Homestuck}}''
** Inverted: [[spoiler: Gamzee Makara]] begins with the stable merged personality [[spoiler:when stoned]]. Then he [[spoiler:sobers up]], the personalities split, and both of the resulting personalities are AxCrazy.
** [[spoiler:When Jade Harley ascends to the God Tiers, she's merged with her dream self which had branched off into its own different personality, Jadesprite, for a time.]]
** This apparently was to be the destiny of [[spoiler:Calliope and Caliborn]] and it is implied to be part of the natural lifespan of their race, [[spoiler:the cherubs]]. Sadly [[spoiler:Caliborn managed to kill Calliope's dream self]] meaning that they will remain as fractured personalities forever.
* Attempted a few times by ''Webcomic/{{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 [[spoiler: they were actually copied]]. Another time a psychologist tried to get her personalities to destroy each other.

[[folder:Web Original]]
* Happens to [[spoiler: Sasha and Abby when Sasha dies while mentally linked with Abby]] in the Podcast/MetamorCity novel ''Making the Cut.''

[[folder:Western Animation]]
* Mike in the ''WesternAnimation/TotalDramaAllStars'' finale, after hitting the ResetButton, not only loses his other personalities, but also gains the abilities of his other personalities, except for Mal's.
* ''WesternAnimation/RickAndMorty'': In the episode "Rest and Ricklaxation", Rick and Morty get split into "healthy" halves and "toxic" halves. Rick realizes they have to merge back to save the lives of their toxic halves,[[spoiler: but Morty refuses to do so and runs away. Eventually Rick tracks him down and forcefully remerges him.]]