Pushing a new character into the spotlight via Character Derailment of the character that they're replacing. Dying to Be Replaced seems merciful and dignified by comparison. At least that way you're dead, or comfortably converted to The Dark Side, before someone starts messing around with your job.
The "victim" who was Dying to Be Replaced is moved out of the way, but the victim who is Not As You Know Them is expected to stick around and suffer. Not only have they lost their old title, it's usually through circumstance rather than their own fault. Unfortunately, whatever happened to them has transformed their personality - generally into something more jaded. They're still there in the story, they're still (usually) on the side of good... but for all intents and purposes, it may as well be a different character. They often become a Cynical Mentor to the new hero, who, of course, is much better at their job than they ever were.
It's a trick that writers use to keep people tuned in to the show/playing the video game/reading the books when they decide to switch protagonists. Rather than risk starting all over again with a new character, the writers use the old hero as a hook to lure in the "old faithfuls" in the audience. Unfortunately, many fans have become wise to this ploy and view such sequels with some trepidation. It's a bit of a Catch-22 - do you avoid knowing your favorite character's fate, or find out what happened to him, at the risk of realizing that you don't particularly like what's happened to him?
So why do a character assassination on an old favorite? Well, if the returning character was as lovable as (s)he originally was, the viewers' familiarity with them means that audience allegiance would remain firmly on their side... even when they're going against the new hero. That's not what the writer wants — they want you to follow the new guy, so the returnee is demoralized to alienate them from the viewers/readers. However, this can backfire if the viewers resent the newcomer already, just for being a "usurper", and then find insult added to injury when they find their original, amiable hero has become grumpy and surly in the gap between series.
The quickest way to figure out if a character has become Not As You Know Them is to ask yourself "if their physical appearance was completely different, and I wasn't told exactly who they were, would I have figured it out or assumed they were a new character?"
If another character is not benefiting from this character's change in personality, it's a case of Same Character, but Different, NOT this trope.
As is always the case with Character Derailment tropes, Not As You Know Them can be fairly subjective; there will be those who hate the changes and declare Fanon Discontinuity, and those who like them and cite Character Development (albeit Character Development that happened "off screen").
- The most excessive (and infamously so) case may be the prologue to Kyle Rayner's term as Green Lantern, which required a Face–Heel Turn from signature GL Hal Jordan, who in turn either killed or depowered every other member of the Green Lantern Corps. They were careful not to do this when Hal was redeemed and returned as Green Lantern. Kyle got upgraded to "Ion" and was promoted out of the way.
- New Aquaman is in. Old Aquaman gets to be turned into a squid-faced being called the Dweller, whom DC keeps around to keep his fans reading... until he is Killed Off for Real.
- The original Aquaman returns to defend Atlantis in Final Crisis #7... with no explanation given about his death and whatnot.
- And then the original Aquaman was subsequently resurrected as a Black Lantern zombie.
- And then Aquaman officially joined the living. Incidentally, one of the guys at DC said the Aquaman that appeared in Final Crisis was from an alternate universe.
- The original Aquaman returns to defend Atlantis in Final Crisis #7... with no explanation given about his death and whatnot.
- Ryan Choi is the New Atom. Old Atom ran off after his ex-wife (whom he still loved) went crazy/evil. After a "Search for Ray Palmer", the old Atom has been found, but he is now portrayed as cowardly, and eventually this is revealed to be the result of a complicated plot from his nemesis Chronos to discredit him. Then Ryan gets Stuffed into the Fridge and the Justice League: Cry for Justice mini has Ray Palmer torturing a supervillain by shrinking down and stepping on the bad guy's brain. Take note: that's exactly how his ex-wife Jean Loring accidentally murdered Sue Dibny. And this is the same Ray Palmer who in Blackest Night was chosen to be temporarily a member of the Indigo Tribe to help battle Nekron. Each of the Corps are based on a particular emotion, which is how they recruit potential members i.e Scarecrow was made into a Sinestro Corps member due to his obsession with fear. Want to know what the Indigo Tribe's emotion is? Compassion. Possible Fridge Brilliance as Indigo Tribe seems to be made up of brainwashed individuals devoid of compassion, who are infected with it by the rings. People already overly-compassionate wouldn't be able to handle all the extra compassion that the ring comes with.
- The Batman Strikes, the tie-in comic to The Batman gives the usual team-up Poison Ivy and Harley Quinn, but switches the roles around: making Harley the (relatively speaking) level-headed brains of the operation, while Ivy is the unstable one. It helps that Ivy is an impulsive teenager in this continuity, while Harley - while still a daffy hedonist - is a bit more independent and cunning than usual.
- In the last arc of Runaways, Klara was suddenly turned into a psychotic brat in advance of plans to resurrect Gert Yorkes and restore the team to the lineup it had at the beginning of its second volume. When those plans failed to pan out (due to Marvel cancelling the series), Klara was saddled with the comic-book version of PTSD.
- In Fantastic Four, after the writers decided to have Ben Grimm reunite with his ex Alicia Masters, his then-girlfriend Sharon Ventura was given a Face–Heel Turn wherein she made a deal with Doctor Doom in hopes of being restored to her normal form, which naturally caused a rift between her and Ben and ultimately led to her being kicked off the team.
- In The Vision (2015), Victor Mancha was retconned into being a drug-addled thief and murderer who was still fated to become Victorious so that he could be killed off by Vision's wife without imperiling Vision's career with The Avengers.
- Jim Phelps in the Mission: Impossible movies. Peter Graves, who played Phelps in the original TV series, wisely refused to return as the character inexplicably turns evil so the new guy can kick his ass on the way to becoming the new main character.
- In the The Last Jedi, Mark Hamill returns as the iconic Luke Skywalker after 35 years offscreen, only for fans to find him very different than he was at the end of Return of the Jedi, with the film itself suggesting that all of this "Character Development" happened offscreen.
- In the 1988 series War of the Worlds, mercenary John Kincaid joined the cast in the second season to fight alien invaders, and the cast changed as a result. The character he was replacing (Lt. Paul Ironhorse) was kidnapped, replaced with a doppelganger, and then shot himself in the head. Kincaid got more depressed as the series went on, especially when his brother (who he thought was dead) came back - and then died for real. Even the main cast was affected. The lead, Harrison Blackwood, lost his quirky nature, and started carrying weapons, when he refused to do so in the first season, and his accomplice, Suzanne, became so stupid that she didn't know how to bake a cake!
- Chloe Sullivan suffered from this during the 7th season of Smallville, once Lois Lane was hired at the Daily Planet in a chain of events that led to Chloe being fired by Lex Luthor for protecting Clark. This came a few episodes after she had gleefully handed over all her info she had compiled through investigation on the Luthors to Lois.
- From Merlin: After several years of being terrorized at the hands of Uther and being poisoned by Merlin in a somewhat misguided attempt to save Camelot from a sleeping spell, Morgana leaves the show under the protection of her half-sister Morgause. At some point the writers must have felt that all she'd suffered through made her too sympathetic, and so went out of her way to make her a sneering, smirking super-villain in series 3.
- Andy Bernard suffered this in the 9th season of The Office (US) as part of a writer attempt to shill two new characters - Nellie and Pete. Andy had perfectly legitimate reasons to hate Nellie (who had stolen his job the previous season) but the writers apparently forgot this and consistently portray her as The Woobie and him as a bully. Pete meanwhile simply steals Andy's girlfriend Erin and is portrayed as a much better partner, Andy having suddenly lost all sensitivity towards Erin when as recently as the 8th season he had broken off a relationship with another woman to be with her.
- Kes of Star Trek: Voyager was written out of the show early in the fourth season as having Ascended to a Higher Plane of Existence. But then in season 6, she's back in her physical body and out for Revenge on Voyager thanks to not remembering she'd left on her own, killing B'Elanna, not listening to anyone, and trying to abduct her younger self. Quite the opposite of the entirely good-natured person she was while on the crew.
- Season 4 of The Librarians 2014 reintroduces Nicole Noone, Flynn's original Guardian from The Librarian: Quest for the Spear. Not only is she played by a different actress, she's a crazed immortal who is convinced the Library can't be trusted and has a Batman Gambit to destroy it. Because Flynn has a new Guardian now.
- Tales of Symphonia: Dawn of the New World supposedly features Lloyd as an antagonist. The opening has him killing people in the burning ruins of what had been Palmacosta. Your first few encounters place him as either crazy or evil. it is later shown that this was an impostor. You then meet up with the real Lloyd who, while changed, is clearly not with the bad guys.
- In Mega Man X7, the reluctant warrior X is suddenly an obstructionist pacifist so that Axl can steal the show.
- Subverted in Mega Man Zero when X appears to be the antagonist, but it turns out to be an impostor, and the real X is a cyber elf.
- In Deus Ex: Invisible War, the hero of the original Deus Ex has been converted from a badass secret agent with a practical take on geopolitics, to an intellectual super-being with a god complex who wants to reshape the world in his image. He's also the Final Boss in every ending EXCEPT for the one where you side with his faction.
- Justified, he had his mind merged with an AI programmed to reshape the world in its image. It's also complicated by the fact that players were able to determine his character in the first game — playing him as an intellectual super-being with a god complex was entirely possible.
- Dreamfall, the sequel to The Longest Journey, brought back the heroine of the previous game, about thirty years older and absurdly cynical and bitter. She was still the most appealing main character in the game.
- Contra: Shattered Soldier plays this straight: Lance Bean, player 2 in the early Contra games, was apparently killed off between games (causing him to be replaced by Lucia, a female protagonist), only to be revealed that he still alive and is in fact the terrorist leader (the game attempts to justify by this by revealing that Lance is a Well-Intentioned Extremist who was fighting against the evil masterminds actually responsible for the Alien Wars). Neo Contra lampshades by having Lucia, Lance's replacement, do a Face–Heel Turn herself.
- In Pokémon Gold, Silver and Crystal, you play as a new character. However, deep inside the final dungeon of the game, you find the player character from the original Pokémon Red, Blue and Yellow, who elsewhere in the game is stated to have been missing for years, simply standing there on a cliff staring at the sky and not speaking to you before or after he battles you (with what are far and away the most powerful Pokémon owned by any Trainer in the game). Some would argue that the lack of speech is simply because he is a Silent Protagonist in the original games, though in fact the dialogue of other characters frequently implies that your character actually spoke but you simply didn't see it directly. Game Freak would stick to Red "speaking" in Visible Silence for his later appearances note , likely for nostalgic purposes.
- In ObsCure II, Shannon, Stan, and Kenny, the three returning protagonists from the first game, all underwent some severe personality changes in the two years since then. It's most notable with Shannon, who went from a cute, brainy Girl Next Door to a hot goth chick who Took a Level in Jerkass. It's slightly more justified for Stan, the pot-smoking slacker whose time in prison likely gave him his new attitude, and for the former varsity athlete Kenny, whose Face–Monster Turn halfway through the game is justified by his running out of the medicine he needed to keep his mortifilia infection at bay. Still, it's obvious that this was done to make room for Amy, Corey, and Sven, who have similar character traits to those that Shannon, Stan, and Kenny respectively had in the first game.
- [PROTOTYPE 2] replaces protagonist Alex Mercer with new character James Heller, a move the developers made to avert Bag of Spilling and in the hopes Heller would gain more audience sympathy. In the process, they decided to make Alex the villain — by completely inverting his personality and ignoring most of the last game's plot developments. Where Alex once went on a vicious Roaring Rampage of Revenge against those he perceived as responsible for New York's hellish state, killed Greene to stop the infection, and blew himself to pieces preventing New York being nuked, he's now deliberately spreading the infection (including to Heller), making rambling speeches about humanity's worthlessness, working with plants in GENTEK to make the virus more powerful, planning to infect a pre-pubescent girl to create a new "Greene"... Even reading the bridging comics makes it only slightly less difficult to believe they're supposed to be the same person.
- Both Anders and Justice in Dragon Age II. When introduced in Dragon Age: Origins – Awakening, Anders was a free-spirited and carefree mage while the Spirit of Justice was, true to his name, a Knight in Shining Armor inhabiting a decaying corpse. Between the events of both games, Anders takes Justice into him and becomes an Abomination and both of them change incredibly. Vengeance is no longer concerned with doing general goodwill, but on avenging the mages that it feels are oppressed, while Anders loses most of his humor and concerns himself entirely with the plight of mages. Over time, the two become increasingly more obsessed with bringing down the Circle of Mages and the Templars, culminating in blowing up the Chantry to invoke a war between them.
- Harvest Moon: Back to Nature shares the same characters with ''Harvest Moon 64' but the way they're presented is highly different. For example:
- Elli in 64 is the Girl Next Door type who works at the local bakery. She is canonically overweight due to her Sweet Tooth and is insecure about it. Elli's parents were fishermen and died in a storm. She now lives at the baker with the owner Jefff and her grandmother Ellen. She goes through an important character arc later in the game when her grandmother dies, and she must overcome her sorrow at losing her only remaining family member. Elli loves baking and fishing, and is often out by the river. Elli in BtN is a nurse who takes healthcare very seriously, and is no longer overweight. She works in the clinic with the Doctor, and lives in the village with her grandmother Ellen and her younger brother. Elli and Stu's parents died prior to the game due to unknown reasons. Elli admires the Doctor for his medical skills and is also in love with him.
- Popuri in 64 lives with her parents in her mother's flower shop in town. Popuri's dream is to cover the world with flowers, like her grandmother Nina. Popuri takes flowers and plants very seriously. She has a father complex as her dad is gone for half the year. Because of this Poppuri often acts childish, since her father babies her when he is around. In BtN, Popuri is the spoiled little sister of Rick who lives at the chicken farm with her mother. Popuri's father left a long time ago to search for medicine for Lillia but has never returned. This has caused Rick to assume the role of "man of the house." Popuri wants to be something more than a meer chicken farmer and is attracted to Kai, who will take her away with him if the two get married. Popuri loves chickens and some of her favorite gifts are eggs as well as flowers.
- Karen is an aggressive woman who lives at the Vineyard, with her drunkard father Gotz (who is implied to be abusive) and her depressed and reserved mother, along with their field worker Kai. Karen wants to get out of the country and see the city but she also loves the vineyard and dreams of restoring it to its former glory from the days of her grandmother, Eve. Karen likes to drink, which is implied to be mostly due to drowning her sorrows, and works in the bar at night. Karen in BtN is a laid back, casual girl who lives at the grocery store with her weak-willed father, Jeff, and her overbearing and outspoken mother. She still likes to drink, but does not work at the bar and doesn't have a reason behind it other than liking it. She is childhood friends with Rick and tries to make him see how unreasonable he can sometimes be. Karen is a Cool Big Sis figure
- Mary (or Maria as she's called) in 64 is a very shy librarian, but will grow more self confidence if you befriend (or woo) her. She is quite religious and likes playing the piano at church. In BtN she's more aloof and reserved than actually shy and lacks the religious aspect.
- Ann in 64 is a loud, playful tomboy who lives, with her dad and her brother Gray, on a ranch. Ann loves animals. Her mother died when she was very young. She knows that her father is worried about her future, thinking that no one will want to marry her because she is so boyish, so she tries to do girly things. However, everything Ann cooks is horrible and will literally make your character sick Ann is a bit rough and has some Domestic Abuse qualities, as she actually hits Cliff if they get married and even you in some events. She is best friends with Karen, and cousins with Rick (both descended from SNES Ann), and hangs out with both of them often. Ann in BtN is a cheerful tomboy from the restaurant, where she lives with her father, Doug. Ann is much more domestic in BtN despite still being a tomboy, and is actually a great cook this time around. She is still insecure about her tomboyishness, and thinks boys will not like her. She's unrelated to Rick.
- Devola and Popola from the original Nier are reintroduced in NieR: Automata, but with notable differences in their characters. This is because they're literally not the same characters, but instead androids from the same production line, working to atone for the actions of the original twins.
- In Apollo Justice: Ace Attorney, the main character of the first three games has been disbarred and become a piano player since we last saw him. His sense of justice takes a battering after this, and he is no longer the upright, optimistic lawyer of the first three games. Stepping up to bat is novice lawyer Apollo Justice. On the flip side, borderline Idiot Hero Phoenix has become something of The Chessmaster in the intervening years, working to reinstitute trial by jury in order to collar Kristoph Gavin, the man who destroyed Phoenix's reputation and plotted multiple murders to keep his own spotless. Considering the way he shrugs off getting hit by a car, one could argue he's been upgraded into a full-blown Determinator. And even without that, he comes back in the game after that as a lawyer again, much the same character he was before, but a little bit smarter and battle-hardened.
- Peculiar example: Egon in Extreme Ghostbusters couldn't really be said to be "not as you know him" - he always was an absent-minded genius, and doesn't change in the sequel series - he's just Older and Wiser. Janine, too, remains much the same personality-wise. However, when the other three original Ghostbusters turn up, their circumstances have changed drastically Maybe Peter's new role as a Hollywood agent was believable, but idealistic, paranormal-obsessed Ray as a salesman qualified as a "huh?" moment. In this case, it's not so much the characters' personalities that have changed so much as their role in life... but since ghostbusting was so central to their character make-up, it's still a culture shock for anyone who watched the original series. It's just as much of a culture shock to the new generation of Ghostbusters as it is to the viewers.
- While Janine may have started off the same, she later got a massive makeover in both appearance and voice. This later became the subject of an entire episode called "Janine, You've Changed!"
- In Transformers: Beast Wars, Optimus Primal was a competent, down-to-earth commander with a tendency to make somewhat sappy speeches. In Beast Machines, Optimus became some kind of spiritual teacher/fanatical terrorist, and the "down-to-earth commander" role got passed to Cheetor, probably the only returning character in the series who didn't get shafted by his personality change.
- Not that Cheetor didn't suffer any. First, he reacted to everything Optimus said as if it was the dumbest thing in the world, even when Optimus wasn't being fanatical, to the point that he reminded you of a certain jet-bot. However, he got better.
- Anyone familiar with The Get Along Gang who watches this pilot for an aborted revival of the series will probably find themselves planting some Epileptic Trees regarding how little Portia Porcupine may have possibly betrayed the original Gang sometime in the past 60 years and is now organizing a new Get Along Gang either to atone for her previous sins or to facilitate a plan against the "common foe" the theme song speaks of...or both.
- In Wolverine and the X-Men, Cyclops is turned into basically the sum of all the bad qualities Wolverine used to have before they made him a Canon Sue (right down to being easily pushed to Ax-Crazy, causing a lot of collateral damage in one episode while raving like a madman.) When he can be bothered to do something other than angst over Jean being missing, his role is "the one who's always wrong so Wolverine can be right." This results in the perfect paragon that is this incarnation of Wolverine being given Cyclops' leadership role in the premiere. This even extends to flashbacks from before Jean went missing: where in the comics (and other versions) Wolverine had been disrespectful to Scott, and openly flirted with Jean even in front of him (to the point that it's hard to know at first if he truly has feelings for Jean or if he just wants to piss Scott off!) the WATXM version has Scott as a possesssive, jealous Jerk Ass who can't stand Logan even saying hello to her, when Logan hasn't done anything wrong.
- Alternate explanation: the writers were simply taking in all of the Flanderization Cyclops has gone through over the years (the nigh-constant Wangst over Jean and his disconnection from the team) and leaving out a fair portion of his honest Character Development that has made him a proper team leader.
- This is pretty much the premise of every character in Harvey Birdman, Attorney at Law.
- In Ben 10: Omniverse, Gwen and Kevin are much different when they return than they were when they left in the first episode, making Rook look like a more compatible sidekick to Ben in the process.
- As with the above example of Wolverine and Cyclops from Wolverine and the X-Men, Batman and Superman swapped personality traits for the fifth season preimere of The Batman, with Batman being the more willing and open to a team-up and Superman being the one who's initially against it.