Works are often adapted from one medium to another. Books become movies, comic books or manga become cartoons or anime, films spawn New Media, and so on, in every possible permutation.
While such Derivative Works generally try to follow the original material with some degree of accuracy, sometimes an adaptation writer will kill someone off for drama, or keep them alive out of sympathy, or just give a clear "alive" or "dead" to somebody whose fate wasn't really specified in the original work.
Normally, this isn't a major issue. But sometimes, the original work is ongoing (or gets a sequel), and at the time, it looked like killing that character or letting them live wasn't a major change — but now it turns out that the character's fate is an important part of the ongoing story. Or the details surrounding it, which the adaptation changed, are critical because there's a Retcon and the character turns out to have been Only Mostly Dead, but the adaptation made that impossible. When this sort of thing happens, the adaptation (or, rarely, the original work) must either do some gymnastics to get things back into sync, ignore it and create an entirely different story, or just handwave the entire thing away.
Like Schrödinger's Cat, the famous thought experiment in which a cat in a box can be thought of as both alive and dead until the box is opened, the character's fate is put into an indeterminate state until the adaptation figures out what they're going to do about the situation.
While this is an adaptation trope, it can manage to show up in original works on rare occasions. For example, if a character is deceased in one part of a Shared Universe (usually their own book), but other works within that universe continue to have them make appearances after their death. Interactive media, such as video games, can also pull this off by having the possibility of several characters dying and changing the plot based on who the player manages to keep alive.
Compare Overtook the Manga, which is more often than not the reason why writers may find themselves dealing with this trope.
When the original author intentionally leaves story elements indeterminate so he can figure out what he really wants to do with them at a later date, see Schrödinger's Gun.
- Abberline of Black Butler gives a tragic, Ciel-traumatizing Heroic Sacrifice in the anime... only to drop in to say hello in the manga chapter that came out the month of his death. Oops. The anime fixed this by having his hereto unmentioned twin brother appear in season 2 and take his place. Also happens to Ciel himself. The first season of the anime ends with Ciel being taken into the afterlife by Sebastian to have his soul harvested, with the final shot being Sebastian moving in to take it. Cue season 2 and he's a Boy In A Box, and it's not until several episodes later that we find out exactly what happened to cause this.
- The anime of Bleach introduced the three Modsouls in its Bount filler arc. This led to a problem when they returned to the manga storyline, since those characters don't exist in that plot. The solution seems to be only including the Modsouls in scenes that contain Kon; as he's already a comic relief character with little impact on the plot, it doesn't really affect anything to make it an ensemble of comic relief characters.
- The Modsouls show up in a larger role, including their formidable combat abilities, during the short segments of filler used to pad out actual arcs, such as during the begining of the Hueco Mundo arc.
- The Bount filler arc was based on manuscripts by the original author that he ultimately chose not to use in the manga continuity. However, the author borrowed some of the ideas from his unused (at the time) writing later in the manga. This resulted in some Narm when, in the anime, Ishida loses and recovers his Quincy powers for the second time. It's hard to take his angst seriously, especially since he was even more over-the-top with it the first time. This was lampshaded with a What the Hell, Hero? moment in the fillers.
- In the Cardcaptor Sakura anime, Mei Ling was an added character who followed Syaoran as his self-declared fiancée. Her major problem is, since Syaoran ends up with Sakura, their relationship is doomed and the plot can't accommodate her. She was Put on a Bus, with the insinuation that their engagement wasn't entirely official, making fans wonder why a Muggle like her was allowed to follow him to another country in the first place.
- In the original Cutey Honey manga, during Panther Claw's attack on Honey's school, Alphonne and Miharu are explicitly killed along with most or perhaps all of the student body and their deaths are Played for Laughs. In the anime version, Alphonne and Miharu explicitly survive along with most of the student body. This is probably a good thing, since the anime version filled them out more as comic relief characters and gave the audience time to develop affection for them, so killing them off so unceremoniously would have felt inappropriate. The anime deals with their presence by just making sure they don't really impact the plot. They can just lurk in the background.
- The first season of the Detective Conan anime was so determined to remove the Black Organization that multiple Adaptation Induced Plot Holes were created when the anime was forced to line up with the manga. In episode 12, the animators changed the villains from The Syndicate to some generically bad guys who, among other things, attempted to murder their employee, Akemi Miyano. However, later on, it turned out that Akemi's death at the hands of the Black Organization was an important motivation for a new character: Ai Haibara, the younger sister of Akemi. As a result, the anime wrote a filler episode that had her Killed Off for Real, this time by The Syndicate. Ran hung a lampshade on this by asking Conan, in a confused voice, if they'd seen the victim somewhere before.
- In the 2003 anime adaptation of Fullmetal Alchemist, Shou Tucker and Tim Marcoh swapped roles, more or less. In the 2003 anime, Marcoh only has one major appearance before being killed off screen, but in the manga he survives and shows up later in the story as an important character. Conversely, in the manga, Shou Tucker is killed by Scar after one appearance, but in the anime he comes back later to more-or-less fill Marcoh's role, except where Marcoh's story is full of self-loathing Angst and atonement, Tucker's is full of insanity, weirdness, and an upside down head. By that time, though, the anime is deep in Gecko Ending territory and is paying no attention to the original manga.
- The Galaxy Angel gameverse killed off Eonia at the end of the first game. However, the manga kept him around and eventually made him the Big Bad of the next arc, possibly to avoid dedicating any more plot space to the ever-expanding conspiracy that unfolded in the games.
- For Gundam fans, there's been a debate that's raged since the late 80s: did Amuro Ray and Char Aznable die in Char's Counterattack? Yoshiyuki Tomino's Word of God is that, in his mind, they are dead — unless Sunrise puts them in a new story set post-CCA!
- This wound up happening and was answered somewhat in the Mobile Suit Gundam Unicorn OVA series, which seems to establish that at least Amuro really did die, since he appears as a Spirit Advisor to the main character. With Char the jury's still out.
- Gundam has another rather famous example: In Tomino's novelization of the original series, Amuro gets killed during the final battle; rather than his trademark Kill 'Em All nature, Tomino has said he did it because he didn't think there would be any sequels and wouldn have had Amuro live if he'd known otherwise. When Zeta Gundam rolled around and Amuro has an important role, Tomino's novels simply reflected the anime continuity where he was still alive and well.
- In the last episode of the first season of Gunslinger Girl, Angelica is implied to have died, which does not happen in the manga which the show is based on. Since the second season largely follows the manga, Angelica is up and about again, apparently indicating that she got better.
- Magic Knight Rayearth
- The character of The Blacksmith Presea was killed off for drama in the first season of the anime, but wasn't in the manga. Unfortunately, she was a required participant in the second season. At first they tried to explain that she was resurrected, but this broke a cardinal rule that CLAMP has for their worlds. So the person who the Magic Knights thought was Presea was really her twin sister Sierra, also The Blacksmith (though her abilities were slightly different), who just happens to know everything that Presea did and can imitate her precisely, including her mannerisms, and everyone who knew went along with it so that the Magic Knights wouldn't feel bad.
- Inverted with Ice Sorceress Alcyone, who is killed off by Zagato, after begging him for her life, on her knees, while also telling him how much she loved him; given what we learn of his true intentions, he pretty much wasted her for nothing. In the anime, she hangs around Emeraude's castle till the end of the first season, disappears mysteriously, and comes back as The Dragon for the Big Bad Debonair (who ultimately does kill her).
- The Mai-Otome Zwei manga ignores the preceding Mai-Otome manga, instead being a sequel to the anime. This is presumably because the Mai-HiME franchise is one big example of Anime First.
- In The Day of Sigma, the tie-in OVA prequel to Mega Man: Maverick Hunter X (the Mega Man X1 remake for the PSP), Dr. Cain is killed during an explosion. However, in the original SNES games, Dr. Cain was still alive as of Mega Man X2. Apparently there were plans to remake the whole SNES series on the PSP to conform with the new continuity, but the low sales of Maverick Hunter X prevented that from happening.
- Nasuverse visual novels have this trope virtually built in when sequels come about, without even being adapted to another medium. Their visual novels can have as many as a dozen possible endings, with different endings having different characters live or die, so making a sequel gets very tricky. This is usually handwave with some mumbling about alternate universes. (There is no ending of Fate/stay night where everyone lives, which could have acted as a canonical ending for sequels to build from — but it's okay, it's a crazy-anything-can-happen singularity universe!)
- Ranma ½
- Voodoo-obsessed Hikaru Gosunkugi from the manga was eliminated when the series was animated. However, several plots in the second season required someone to serve in the same role; thus Sasuke, the ninja houseservant to the Kuno clan, was introduced as a replacement. Eventually, Gosunkugi did appear in the anime, several seasons along, but as a somewhat more sympathetic character who even got his own brief romantic Story Arc — with a ghost.
- A bizarre example that doesn't involve a character's life and death revolves around public knowledge of Ranma's curse. In the manga, the whole school found out relatively early on that Ranma can change into a girl. In the anime, however, his classmates never found out about it until near the end of the series, when Genma entered the scene out of nowhere and proceeded to pretty much spell it out to them for no apparent reason.
- The second season of Rozen Maiden veers away from the manga quite a bit... however, near the end, numerous rapid-fire deaths and resurrections occur in order to synchronize with the end of the manga.
- Sailor Moon
- The Death Busters group of villains from the third arc is quite different in the anime than they are in the manga. Especially Professor Tomoe, who was originally a straightforward Mad Scientist. In the television series, he was filled out and became a quirky and nuanced looney with a sympathetic reason for his actions. However, the later arc of both versions requires Hotaru's presence with the Outers. Since he wasn't killed off as in the original version, Sailor Pluto simply "borrows" Hotaru from him in a flashback, and he disappears from the face of the Earth.
- Sailor Pluto's own death occurs at a very different time in the two versions, partly because the plot arcs for Chibiusa were also modified. This was, for simplicity, outright ignored in The Movie adaptation.
- Queen Nehelenia is probably the biggest example, as her original manga incarnation was directly tied with Sailor Moon's origin, her mother, and the series' Bigger Bad, whereas the anime version is a less important but more human kind of evil.
- Buttatake Joe of Soul Eater survives in the anime, but because Justin Law was his murderer and they couldn't do The Reveal, the anime had to take another route. BJ's survival effectively marks the point where the anime diverges into a Gecko Ending. Sadly, BJ doesn't even get his dream girl back in the anime.
- The last episode of the first season of Tsubasa -RESERVoir CHRoNiCLE- was a filler episode where Sakura made a wish from a god to bring a number of people Back from the Dead. Unfortunately, this became a major conflict with the Aesop that CLAMP made in the part of the manga that would become the second season — Gods and wishes cannot bring people Back from the Dead as they were. Bee Train, the anime production company, had to make an Author's Saving Throw and had the characters return to the world where the events happened, to explain that the wish had resulted not in true resurrections, but in "physical ghosts" that would vanish after a month.
- Xenosaga: The Animation kept Lieutenant Virgil alive through most of the series, while he had died in the first segment of the game. Oddly, the manner of his death was unchanged, just the timing of it.
- In the manga version of Yu-Gi-Oh!, Bakura kills Pegasus in the process of stealing his Millennium Eye, while in the anime version Pegasus loses his eye but survives, and appears later as a secondary character in Filler arcs. This event seems to separate the anime and manga into separate continuities, as Pegasus appears in the anime version of Yu-Gi-Oh! GX, but his death is an important part of the manga Yu-Gi-Oh! R.
- Ms. Marvel was (temporarily) killed in her own title when her powers overloaded. Apparently there was some internal confusion on this point, however, because she continued to appear in the New Avengers title as if nothing had happened!
- In the Transformers series, Ravage appears and dies in the second movie. However, the post-movie comics were already planned before that plot point was finalized. So yet again, Ravage comes Back from the Dead in the comic continuation of a screen story where he was intended to truly be dead. This is one cat who always lands on his feet! However, Soundwave can't sense him, and he can sense all the rest of his underlings, which suggests that Ravage Came Back Wrong.
- The Aliens comic series by Dark Horse originally started as a sequel to the events of the second movie. Since Ripley couldn't be used due to stipulations from the movie executives, the writers decide to focus the comic around Hicks and Newt. When Alien³ unceremoniously killed off Hicks and Newt (and ultimately Ripley herself), the comics were reprinted with the characters renamed.
- Ian Malcolm survived in Jurassic Park, while in the book he died. Then as Michael Crichton was told to write a follow-up, The Lost World (1995) has Malcolm showing up alive, attributing his not-being-dead to several accounts of the events; evidently the first book was one of them, being either incomplete or inaccurate. Fortunately, it wasn't much of a retcon; his death in the book happened off-screen when he succumbed to his wounds at the very end. On a lesser note, John Hammond was still dead in the book, even if his Spared by the Adaptation status led to an appearance in The Lost World: Jurassic Park.
- Who Framed Roger Rabbit is very different from the book Who Censored Roger Rabbit?, in which the titular character dies at the beginning and is represented for the remainder of the story by a "temporary stunt copy". The second Roger Rabbit book ignores the first book's events entirely, instead acting as a sequel to the movie. The first book is handwaved as being Jessica Rabbit's dream.
- Robert Crumb killed off his Fritz the Cat character after he was disappointed with Ralph Bakshi's movie version. Steve Krantz, the producer of the first film, made a sequel anyway, without Bakshi, titling it The Nine Lives of Fritz the Cat.
- In both the original novel and film of Layer Cake, the protagonist gets shot at the end of the work. In the former, he survives. In the latter, he is implied to die, but it's deliberately ambiguous. If the novel's sequel is ever filmed, then he'll obviously be alive in both works — but until then, the film version is left unclear.
- Christine's father Richard Bravo is alive and well in the play and movie of The Bad Seed, but had died before Rhoda was born in the book.
- In the Harry Potter books, Lavender Brown's status at the end of Harry Potter and the Deathly Hallows is so unknown that even Pottermore lists it as "unknown". In the film, she is not quite so lucky.
- Knots Landing was a spin-off of Dallas; the main character of the spinoff was Gary Ewing, the black sheep of the Ewing family. Gary fathered a pair of twins right as his brother Bobby died on the parent show, and so he named his son after his dead brother. A year later, Bobby was brought Back from the Dead as the entire previous season was retconned away into a dream. On Knot's Landing, Bobby Ewing stayed dead. (Which, weirdly, implies that the spinoff show takes place entirely in a dream-world...)
- The House of Cards (UK) trilogy continually foiled novelist Michael Dobbs' attempts to give Villain Protagonist Francis Urquhart his comeuppance, notably at the end of the first series when, instead of plummeting to his death, he commits casual murder and evades justice. Dobbs went with the flow and each novel in the trilogy follows on from the TV adaptations rather than the other novels.
- Largo Winch was adapted from the Largo Winch comics to live-action, which led to a number of composite characters, canon foreigners, and so on. By necessity, the TV show is assumed to just be an unrelated alternate universe. It does get a little weird when a traitorous Corrupt Corporate Executive from the comics shows up as an obnoxious but honest guy in the TV version.
- In the original Kamen Rider TV series, Takeshi Hongo (the original Rider himself) was written off and replaced with Hayato Ichimonji (Kamen Rider No. 2) after Hongo's actor Hiroshi Fujioka broke his leg while performing a stunt. Since Fujioka's return to the TV series was uncertain at the time, his manga counterpart was killed off for dramatic purposes. When Fujioka returned to the show completely fine, Hongo returned to the manga as well by revealing that his brain was extracted from his corpse and implanted into a robot body.
- The Walking Dead follows the comic's storyline in Broad Strokes, but frequently switches around character deaths to preserve its Anyone Can Die status and maintain an element of surprise for comic readers. In later seasons the show's cast only vaguely resembles the comic's, as many important comic characters died early on while originally minor characters (and a few Canon Foreigners) went on to become members of the core cast. While the show tries to include all of the character arcs from the comics, many of them are given to different characters and sometimes edited to account for new circumstances, or just to keep things fresh.
- Geese Howard in Fatal Fury and The King of Fighters. In Real Bout Fatal Fury, Geese unquestionably dies in a fall from Geese Tower, setting up his son Rock's storyline in Mark of the Wolves. In The King of Fighters, Geese is alive and a playable character in a few titles. Then there's the Maximum Impact series, a third continuity that has Geese dead — Billy Kane appears in the second game, and his storyline revolves around avenging Geese's death by defeating Terry Bogard. Geese is playable as well, but in his "Nightmare Geese" form, which only appears in games where he is canonically dead.
- Notably averted in Tales of Destiny, in the case of fan-favorite Leon Magnus, who dies in every adaptation of the game, whether it's the Drama CD, the manga, a part in a crossover game, the remake or even the Updated Re-release of the remake that features his own story mode. He ends up dying without fail every single time, though often under different circumstances. In Tales of Heroes: Twin Braves, another crossover, Stahn's scenario also involve Leon dying in a Heroic Sacrifice like in the remake. But then it's suddenly revealed, in the very next scenario, that he avoided death thanks to Yuri Lowell saving him in the nick of time. He rejoins Stahn to finally get a happy end, making it a long-desired aversion.
- The arcade version of Double Dragon II The Revenge revolves around the Lee brothers going off to avenge the death of Marian, who is gunned down by the Black Warriors in retaliation of their defeat in the original game. The plot is similar in the NES version, except the ending was changed so that the game ends with Marian being restored to life. When the third game was later released for the NES under the title of Double Dragon III: The Sacred Stones, the English localizers took advantage of Marian's survival in the previous NES game and changed the identity of the final boss from a resurrected Cleopatra to a possessed Marian.
- In Fire Emblem Fates, the survival of different characters affect certain aspects of the story, up to and including the survival of certain recruitable units. Most character deaths are unavoidable on specific routes, but some can be prevented.