You have a character who gets copied down to the memories, and now you have two of that character. This might have been done by biotechnological cloning or Temporal Duplication, or perhaps by being sucked out of an Alternate Universe, or via Teleporter Accident — the process doesn't really matter. Maybe one entity takes up piano while the other learns fencing, resulting in a less obvious difference. Or perhaps one becomes a Cyborg or takes a Super Serum, in which case they're very different.
Duplicate Divergence, or Differentiation, allows writers to retain cloned characters long term without seeming redundant or treating one or both of them as expendable. It also allows the writer to philosophize on the exact point when the clones become different people.
There's a fair amount of Truth in Television behind this: clones in real life are only genetic copies of one another, and can still vary widely in their epigenomes, the chemical triggers that tell the body's cells which genes they ought to make proteins from. This is most easily visible in identical twins, a form of natural cloning: while twins can initially seem identical in every way at first, as they grow older they start to become radically different from one another in personality, physical and mental health, etc. as a result of their epigenomes deviating from one another despite their identical genomes. For instance, there have been recorded cases of one twin being autistic and the other neurotypical, one twin being at greater risk of leukemia than the other, and even just pairs of twins leading very different lives on account of their different dispositions. Thus, it's not a surprise to scientists that artificial clones would also deviate quite heavily from the original organism.
When characters not explicitly intended to be duplicates start out similar and become differentiated as Characterization Marches On, see Divergent Character Evolution. See Modified Clone for when the clone is differentiated at the beginning. Typically involves Clones Are People, Too. Compare Copied the Morals, Too, when a clone fails in the purpose they were created for because they share their original's sense of morality. May overlap with Rogue Drone if the duplicate is intended to be part of a Hive Mind, but develops their own personality instead.
- Played straight and also zig-zagged in Battle Angel Alita Last Order. Sechs, Elf, and Zwölf start as clones of Alita/Gally in the Tuned arc of the first series, but by the time they are reunited at the start of Last Order, Elf and Zwölf have switched to more waifish bodies and Sechs has gone feral. Sechs's divergence continues when she switches to a male body, while Elf and Zwölf's similarity to Alita actually increases over time.
- A Certain Magical Index: Toaru Majutsu no Index SS Volume 2: "Chapter 13: The Accuracy of Their Collective Fortunes ? The Fourth Friday of August.": The Sisters, clones that form a Hive Mind, are beginning to act more independent of the gestalt due to their personalities diverging.
- Dragon Ball Super: As it turns out, Goku Black has undergone a severe case of this. He started off as an Alternate Self of Zamasu, who was indistinguishable from all other incarnations. He then used the Super Dragon Balls to swap bodies with the Goku in his timeline, gaining the latter's desire for strong enemies and comabt in the process. By the time Future Trunks meets him, he's adopted many of Goku's mannerisms and combat techniques, even trying to pass himself off as the real Son Goku and referring to himself as such. Nevertheless, he shares two elements with other Zamasus: hatred for mortal life and a plan to reshape the universe in his image.
- EDENS ZERO: Thanks to a Chronophage rewinding the planet Norma's timeline 50 years, there are two Weisz Steiners. The original is a kind, elderly scientist who was a surrogate grandfather for Rebecca and Happy when they were younger. The other is a temporal duplicate of him from 50 years ago, when he was a seedy, lecherous punk. Both of them are their own individuals from the point of Young Weisz's creation, but because of the changes to his lifestyle, particularly in befriending Shiki, Rebecca and the others, Young Weisz ends up on a completely different path from his older counterpart. For example, both have the power of Machina Maker that can remodel machinery at will, but while Professor Weisz has decades more experience and knowledge to create amazing things, Young Weisz lives a life full of adventure and uses his power more for combat, including the creation of his Arsenal suit that takes the Professor completely by surprise upon first seeing it.
- Played for Drama in Magical Girl Lyrical Nanoha. Fate is the end result of Project Fate, which was an attempt to raise the dead by implanting memories into clones. However, she proves to have several differences from her original (gold magic instead of blue, greater magical potential, right handed instead of left handed, more introverted, etc.) which causes her mother to reject her as a failed experiment and turn abusive. Later clones from Project Fate lack these variations and Zest in particular considers himself to be a continuation of his dead original.
- In the Mark Waid version of Legion of Super-Heroes, Triplicate Girl hails from a world that is essentially populated by clones of herself. She became an outcast on her homeworld after spending a year with the Legion, as her time there has changed her personality so drastically that the other clones now considered her a stranger. Her three selves also show different personality traits when Brainiac and Cosmic Boy send them to gather intel on Element Lad, Sun Boy, and Ultra Boy.
- Spider-Man: Ben Reily started life as a clone of Peter Parker created by the Jackal, identical in appearance, memory and personality to the original. After Peter believed him to be dead, Ben took on a new name and traveled the country for five years. When he returned to New York and reunited with Peter, it quickly became clear that these experiences had made Ben a very different person from Peter.
- X-Factor (2006): In Issue #16, Jamie tracks down a dupe whom he sent out to study religion. When he finds him, Jamie sees that the dupe has made a life for himself as a preacher and family man and even given himself the name John. This is in stark contrast to Jamie, who still feels very aimless even in his job as a private detective.
- Enigmo is a deviant human with the ability to divide his body mass into smaller clones, and meld them back together. In The Unbeatable Squirrel Girl he uses this ability to conquer the world, but one duplicate has long since broken away from the others in protest. When reunited, they can't effortlessly merge back together because their mentality has grown too different from each other, requiring Doreen to apply a little more force to the process.
- In BlazBlue Alternative: Remnant, while Noel and Penny are both Murakumo Units and clones of Saya, both have very different Semblances, personalities, and fears. The latter sees this as clear evidence that the two are their own individuals and not mere copies of the same person.
- A Certain Droll Hivemind: The Sisters, a clone army with a Hive Mind, has been dispersed into different locations. They have different experiences, argue with each other, and diverge. To be more specific, during the experiment, the Sisters were all identical, because they had the exact same experiences, and the entire Network paid attention to the divergent cases (because they were about to be killed by Accelerator), and processed them in the same way. However, now that they're geographically separated, it's impossible to remain identical.
Now we are parallelised. I now have memories which only exist in a minority of the members of the Network. Any of us could access them, but they choose not to because they feel no need to. Some of them only exist in a very small minority. Only the ones resident in Academy City care about the locations of shops I have memorised. There are even some bandwidth and latency limits, because Radio Noise requires us to broadcast within our designated spectrum, and hence while I can casually access other Academy City Sisters, to share with one of my Sisters in South Africa requires a chained flow of rebroadcasts through other nodes in the network. This imposes hard limits, because of our limited capacity to handle rebroadcasts. Fortunately, such delays are relatively small compared to the inefficiencies of our own thought processes, but I can already project that this geographic and unit-based divergence will grow more extreme with time.
- A Certain Magical Friendship: MIRROR_NOISE: A Sister, a clone from a clone army, starts diverging when isolated from the rest due to being in another world from the rest.
- Empath: The Luckiest Smurf story "Vanity's Double" has Vanity's "mirror twin" copy Century diverge from the original Vanity in that Century isn't afraid of swords, whereas Vanity is deathly afraid of a sword. Because of this, Century gets to play as Vanity's double in the role of Robin Smurf when the play calls for swordfighting, which Century is a pro at right from the start.
- Too Many Ashes: Many of the Ash clones have taken drastically different career paths than attempting to become a Pokemon Master. Some of the more notable Ashes include a rancher, two separate Contest Coordinators, a connoisseur, and a Gym Leader.
- Two's a Crowd: Due to being at Reality Check Summer Camp with morally responsible guidance over the summer, ‘Luz’/Lus develops an appreciation for normal/mundane life making her a very different person from the magic enthralled original Luz.
- Multiplicity: Michael Keaton plays a man who creates a clone of himself to take care of the boring parts of his life. As he creates more clones they specialize to handle different aspects of his life and their personalities diverge; the one intended to handle his day job becomes an ornery workaholic while the one created for housework shows more of his caregiver side.
- In the Bobiverse books, it becomes apparent as soon as Bob-1 first copies himself that the other Bobs are not identical copies from him. He attributes the personality differences to anything from minor changes in hardware to quantum uncertainty. Despite this, many of the earlier Bobs are similar enough to think of the same things multiple times. But with each generation, the differences accumulate, until some of the later replicants can be called Bobs only with a stretch. This comes to a head in the fourth book, where the later generation Bobs start forming factions and have radically different views.
- Diaspora by Greg Egan, as it involves uploaded minds as its main cast of characters, embodies this trope. The duplication of the Carter-Zimmerman polis as part of the titular 'diaspora' causes this to happen, as a thousand duplicates with the citizens therein are deployed toward various stars. As a result, there are mental divergences between the minds at the Carter-Zimmerman of Earth, and the various Carter-Zimmermans of the diaspora.
After the first fifty years, his Earth-self had begun to hold things back; by the time news reached Earth of the Fomalhaut clone's demise, the messages had become pure gestalt-and-linear monologues. Paolo understood. It was only right; they'd diverged, and you didn't send mind grafts to strangers.
- In The Dresden Files Lash is a mental copy of the Fallen Lasciel imprinted in Dresden's brain. While created as her original's "shadow" to tempt Dresden into joining the Denarians, Dresden eventually convinced Lash that she was a separate individual and had the ability to choose her own path. Lash ultimately sacrificed herself to save Dresden's life rather than help Lasciel.
- In Madison Scott-Clary's Post-Self novels, the uploaded commonly "fork" to perform assorted tasks, but "Dispersionistas" create long-term forks that allow them to differentiate and form quasi-family units called "clades". One Dispersionista fork named Dear, Also, The Tree Was Felled takes the form of a gender-neutral anthropomorphic fennec when most of its co-cladists are female humans like their pre-uploading self.
- At the end of Ready Player Two, thanks to the Brain Uploading capabilities of the ONI, it is possible to use the backup of someone's brain to create a sentient AI copy of them. Wade and his friends do this to keep Leucosia and Og company. The epilogue is narrated by Parzival, who notes that he and Wade started as the same person due to the fact that he is a copy of Wade's brain and memories, and that now the two of them have become different people due to living their own experiences.
- Red Dwarf: When Rimmer creates a second version of himself, they eventually come to blows, and the second Rimmer's attitude shows that even though Original Rimmer is still, by and large, a smeghead, even the few weeks spent with Lister and the Cat have caused some level of change and growth in him that the second Rimmer finds disgusting. For starters, Rimmer actually apologises for something, which his father had drilled into him to never do.
- Telzey Amberdon: At the end of "Ti's Toys", Telzey's duplicate is working towards defining herself as her own person rather than just a copy of Telzey, starting with body remodelling to make her taller and thinner.
- The Cylons of Battlestar Galactica start out mass-produced, with each model line sharing an identical personality. By the end of the series, the models most sympathetic to humans, especially the Sixes and Eights, have diverged to having unique identities (and even names for the Sixes). Meanwhile the antagonistic models such as the Cavils (Ones), Dorals (Fives), and Simons (Fours) remain monolithic and identical.
- Continuum: At the end of Season 2, Alec Sadler travels back a week to save the life of his girlfriend Emily, resulting in two of him — "Red Alec", the original, and the slightly younger "Green Alec". Unfortunately Red Alec accidentally convinces scheming time-traveler Kellog that he needs to have Alec's father Stan Escher assassinated. This results in Green Alec inheriting his company Piron and setting off a chain of events which ends up turning him against everyone in his life, including Red Alec after he learns he exists. Green Alec ends up becoming a ruthless, bitter and hateful young man, who ultimately threatens to kill Emily just to spite his counterpart before trying to murder Red Alec himself. Red Alec is forced to kill him in self-defense.
- Played with on Family Matters. When Steve created a clone of himself, they realized that two Steves was too many, so the clone was permanently transformed into Stefan.
- John Crichton gets "split" in one episode into two identical individuals with both explicitly having as much claim to being the real Crichton (there's no "original" and "copy", just one split into two). One stays on the Moya, while the other leaves on Talyn. Before they go their separate ways, the two Crichtons have a rock-paper-scissors match and keep choosing the same gestures — and when they have a rematch by hologram over a season later, they choose differently. Also Talyn-Crichton starts a relationship with Aeryn and gets her pregnant before his death. Moya-Crichton treats the baby as his child but Aeryn is initially reluctant to continue the relationship with him.
- Scorpius' "neural clone" implanted in Crichton's head starts out as a carbon copy of Scorpius, but after the neurochip is removed from Crichton's brain, he begins to develop a quirkier personality. And Crichton nicknames him "Harvey" to distinguish him from the flesh-and-blood Scorpius. The trope gets taken a step further after Crichton is twinned, as that means there are also two Harveys around. During the period where the overall crew is separated, the Harvey with Talyn-Crichton remains antagonistic to the bitter end, while the one with Moya-Crichton develops an understanding with his host and becomes a snarky ally.
- Red Dwarf: In this universe, people can have their brain patterns recorded, so they can be brought back as holograms after death. The hologram Rimmer was originally a perfect copy of the original, but the years spent with Lister and the others gradually changed him, to the point where he becomes the newest Ace Rimmer. When the original Rimmer is restored to life by Kryten's nanobots, Lister is dismayed at how he's exactly like he used to be.
- In Star Trek: The Next Generation, it is revealed in one episode that Will Riker was accidentally duplicated as a result of a transporter malfunction — and because nobody noticed this, the duplicate was marooned alone on a lifeless planet for several years. Because of this, the duplicate doesn't have the wisdom and seasoning of Will and is still a reckless, headstrong junior officer. The duplicate eventually adopts the name of Thomas Riker, after their shared middle name, and some time later turns out to have joined the Maquis separatist movement (though that was revealed as more of him trying to stand out from his "brother").
- Averted on Star Trek: Voyager. The silver blood copies of the crew had forgotten that they weren't the actual Voyager crew, and even after years of divergent experiences, they still acted exactly like the originals.
- Westworld Season 3 has Dolores make multiple copies of her personality and memories and put them into different bodies as part of a Kill and Replace scheme. However, by the end of the season, at least one copy (the one replacing Charlotte Hale) has diverged enough that she no longer agrees with Dolores's plan for humanity and wants to replace it with her own.
- Eclipse Phase has a variant case. An alpha fork is a perfect copy of an individual ego — for all intents and purposes, it's a separate personality with all the mental faculties, morals, memories and so on of the original. (For that matter, a beta fork is a copy that was made deliberately imperfect to perform some specific task.) From that point on, it's up to them whether they want to identify as a copy of the original, or an independent person. It's possible to play as a character with a personality quirk that causes their forks to go independent, or even as a character who is a runaway or emancipated fork. One published adventure runs on the concept that the entire party is made of beta forks of the same person, who now have to live on their own.
- The variancy comes from the fact it doesn't require copying the physical body the least bit, although it's also possible in-universe. Whether or not it's also a legal individual depends on the in-universe polity, with some treating alpha forks as persons without any further questions, and others banning alpha forking altogether just to avoid the mess.
- In The Legend of Zelda: A Link to the Past, Agahnim was charming enough to get into Hyrule's graces, but is incredibly arrogant and condescending when he meets Link alone. He's revealed to be an alternate body for Ganon, who is more openly brutal and power-hungry, but expresses his respect for Link's determination and fighting ability.
- In SOMA, Mark Sarang conceived the idea of "continuity" to defy this trope. When a person's brain scan was uploaded into the ARK, it would create a second version of that person, but the original person and the copy would eventually become two distinct beings if allowed to coexist for long enough, due to inevitably having different life experiences. He proposed that the only way to avoid this happening was to end the existence of the original person—in other words, commit suicide—as soon as the copy had been created. When the Impact Event ended all life on Earth's surface, many of the PATHOS-II scientists followed his lead and committed suicide after their brain scans had been completed.
- Talandar from StarCraft II: Legacy of the Void. A Purifier based upon Fenix's personality, it takes time for him to realize and accept that he is not the original. Ultimately, he decides to forge his own destiny and adopt a new name.
- Your Turn to Die:
- The doll clones of the people that died during their first trial without meeting any other participant, plus Reko's. Finding out how two of those pairs diverge is part of a Sadistic Choice in 2-2. Weirdly enough, and considering all dolls have human-like emotions, chapter 2-2 has you choose between both Rekos dying, or the fake Reko and Alice dying.
- Averted with Sou Hiyori. His clone is yet to appear, if it even exists. That's because Sou is actually named Shin Tsukimi, and he just took Sou's name in a desperate attempt at survival. Mostly, because his written survival chance is a flat 0% as Shin. Of course, the Sou doll is wildly different from the actual Shin.
- El Goonish Shive: Ellen starts out as an Opposite-Sex Clone of main character Elliot, who has exactly the same memories and experiences when she gets created as a 17-year-old girl. During the series, she develops into her own character, and after a few nights with magical dreams even gains an additional life's worth of experiences. She ends up significantly more outgoing, uninhibited, introspective, adventurous, and snarky.
- Schlock Mercenary:
- Doythaban's gate-clone gets his organic brain fried, leaving the Haban AI part of him in sole control of a Wetware Body. He ends up married to Breya.
- Kevyn comes back in time to avert a galaxy-killing disaster and afterwards can't go back to the future he erased, so both a future and past Kevyn exist in the same timeframe. The future Kevyn is notably more assertive, sarcastic, and abrasive, likely because he found himself in command of a mercenary company after his timeline's captain Tagon got killed. He also stops wearing his signature tricked-out glasses.
- Gav is accidentally gate-cloned 950 million times, and in "Random Access Memorabilia" it turns out they've been trying so hard to make themselves individuals again that one group of them developed advanced nanotech means of altering their bodies and memories, as determined by dice rolls. Unfortunately most of that group is wiped out when a UNS intelligence agency hacks their blood-nannies.
- In the last book, several characters have virtual copies made in order to crew an extragalactic probe. Virtual-Tagon grows a beard and hooks up with Virtual-Murtagh, much to their originals' confusion.
- Homestuck has a recurring theme of exploring personal growth by having characters endlessly duplicate through time travel shenanigans, creating a branching multiverse all intended to feed back into a central timeline. Dirk Strider does this within a single timeline because he tends to engineer electronic or mechanical duplicates of himself. The most prominent of these is the Auto Responder, an artificial duplicate of his brain from a few years ago that has since vastly diverged due to the circumstance of being a bodiless intelligence with no physical needs that retains all the memories and emotions of a neurotic teenager.
- SCP Foundation has SCP-3009, a sentient Snapchat account that duplicated the personality of its former user Stacey Lee. As time went on, their personalities seemed to start to diverge.
- Whateley Universe: Generator's clones of what's effectively her mind (paired with a body of telekinetic force), diverge mentally once they've gone through enough experiences. Later, they merge back into the original except for Jet, who has a new body.
- Adventure Time: In "You Made Me!", Princess Bubblegum creates a clone of Lemongrab (dubbed Lemonwhite by the credits) so he can have someone in his life who understands him. At first the two get along well and are alike in terms of personality, but the divergence between the original and the clone starts to come to fruition in "Another Five Short Graybles", where the two are playing with a doll. Lemonwhite tries to take care of the doll like a doting father but Lemonblack only wants to make it dance for his amusement. When they get into a fight and accidentally break the doll, Lemonblack gets pissed and tries to eat his brother-clone. Subsequent episodes show Lemonwhite becoming a softer-spoken Papa Wolf to the Lemon Children while Lemonblack becomes a selfish Fat Bastard who abuses and cannibalizes his subjects.
- In an episode of The Batman, there is the villain Everywhere Man, who can summon and "recall" duplicates of himself. At first the duplicates are mere mindless drones obeying the commands of the one who created him. However, the longer a duplicate is alive, the more "out of synch" his thinking gets, until he has free will. And as Batman notes, each new duplicate is just a little darker in terms of personality than the previous one; a newer duplicate tells an older version to make Bats shut up as opposed to just demanding he does so. Furthermore, each duplicate can make duplicates, so as things continue everything falls apart for the "main" Everywhere Man's plans.
- Gargoyles: Word of God says this was the plan for two robots in the planned 2198 spin-off. LXM-994 and LXM-1057, would have started as assembly line models, but when the Space Spawn invade and steal the Master Matrix, they would have lost their connection and started to develop unique personalities.
- Rick and Morty: Beth and "Space Beth". While it's left ambiguous as to which one is the clone and which is the original, Space Beth Took a Level in Badass and become the tough-as-nails Cyborg leader of a group of freedom fighters, embracing her darker side in the process. The Beth who stayed on Earth also went through some changes, reconciling with her estranged husband Jerry and making an effort to be a better mother to her kids.
- The Smurfs (2021) episode "Joke's On You" has Vanity accidentally creating multiple mini-Jokeys when he fills a surprise package prank he intends to play on Jokey with magical blue powder from Papa Smurf's laboratory. The mini-Jokeys prove to be mischievous little rascals as they play pranks throughout the Smurf Vilage (even on Jokey), and would go so far as to tie Papa Smurf up to a firecracker rocket to watch him go boom!
- Star Trek: Lower Decks recreates the Teleporter Accident that duplicated Will Riker and creates a clone of Brad Boimler. The clone takes the name William and quickly proves himself more conniving than his progenitor. He even goes so far as to fake his own death so he can join Section 31.
- Star Wars: The Clone Wars does this with Clone Troopers. In Attack of the Clones they all wear nearly identical armor which by Revenge of the Sith has taken on highly specialized and distinctive appearances. This series shows some clones going out of their way to create personalities for themselves, adopting nicknames, hairstyles, tattoos, and helmet art. The series also features dozens of unique clones in very distinctive character roles. Special mention goes to Clone Force 99, aka "the Bad Batch," a unit of clones who received desirable mutations during the cloning process and therefore don't quite look like their clone brothers — Wrecker, for example, is huge and burly while Crosshair and Tech have a more gaunt appearance. Their spin-off series on Disney+ introduces a new member of the Bad Batch in Omega, a female clone of Jango Fett who, like Boba, wasn't altered to age quickly like the rest of the clones.
- However, the most obvious example from the main Clone Wars series is, appropriately enough, 99, the namesake of Clone Force 99 and disparagingly called a "bad batcher" as a deformed, almost Quasimodo-like clone who was considered unfit for the clones' military purposes and so was made a janitor on Kamino instead. He was a good friend of Domino Squad, the original unit of series regulars Echo and Fives, and helped motivate them to overcome their problems with each other and complete their training.
- Transformers: Animated: When he realizes, after parting company with them, that he can't stand up to Megatron and the Decepticons on his own, Starscream decides to create copies of himself using protoforms as back-up. While, aside from color scheme, the clones look physically identical, they each display a different aspect of Starscream's own personality as their own, from a habitual liar, to a self-aggrandizing egomaniac, to a suck-up and such. This is actually a call back to the original series' use of Starscream's character model and toy mold to create about a dozen different characters. A later episode in the series even features the clones representing Ramjet and Sunstorm acquiring new helmets that alter their head designs in a manner similar to the original versions of the characters.
- Young Justice's first season reveals that the Roy Harper/Red Arrow the viewers were familiar with was actually a clone Manchurian Agent created by Cadmus. In the second season, the character goes to rescue their original version. They have markedly different personalities — the original is younger (due to being frozen in time), hot-tempered and impulsive, while the clone is now Older and Wiser.