Some element of a show's Applied Phlebotinum causes a character's appearance, voice, and sometimes even their personality to change completely. On Speculative Fiction shows, this can be almost anything. On real-world shows, this is almost always Magic Plastic Surgery — which, on TV, works much better than it does in reality.
This is a catch-all for the recasting of a character using an in-continuity explanation. It takes its name from Doctor Who, whose eponymous Doctor is an alien capable of "regenerating" into a new form whenever he is mortally wounded. This trope, both in the original show and others which employ it, has two benefits; not only can it increase the series' run, it is also a wonderful way to derive drama. With the added bonus of implying that Anyone Can Die, without having to lose major characters.
Compare to: Suspiciously Similar Substitute (which introduces a totally new character much like the old one), The Other Darrin (where the actor is replaced without an in-universe explanation), and Legacy Character (which introduces a different character to the "title" of the previous character).
open/close all folders
In the English dub of Fullmetal Alchemist: Brotherhood, when the homunculus Greed was reabsorbed into Father then brought back into a new body he changed voice actor from Christopher Patton to Troy Baker. Said plot element was in the manga long before the story was adapted into animation and dubbed into English (both had the same voice in the Japanese version) but the timing seems to imply this trope.
Occurs in YuYu Hakusho when Kurama transforms from his human body of Shuichi into his true form of Youko. Whenever this occurred in the Japanese dub of the Dark Tournament storyline, his voice was portrayed by Shigeru Nakahara rather than Megumi Ogata (In the English version, John Burgmeier voiced both forms). Oddly enough, in all uses of this after the Dark Tournament arc, Ogata continued to provide his voice. Although one time it's handwaved by saying that only Kurama's body transformed while Youko's personality hadn't returned, it doesn't explain the other times where Youko's mind clearly does take over.
When Kurama transformed during the Dark Tournament it was because he was subjected to a magical concoction that forcibly regressed him to an earlier point in his life, thereby explaining the resurface of the Youko personality voiced by Shigeru Nakahara. Any time Kurama transformed after that his Shuichi and Youko personalities have completely merged by then, hence the phenomenon of Kurama having his Shuuichi personality while in his Youko form.
In Card Captor Sakura, before he died, Clow Reed split himself into two reincarnations. The first is Eriol, who retains all of Clow Reed's powers and memories but in the form of a 10-year-old boy. The second has none of that power until Eriol reveals the truth and splits the magic in the manga...and he is Sakura's father.
Rogue Assassin had the whole point of the mystery of the eponymous Assassin having plastic surgery to remain unknown. We don't actually see any of the eponymous Assassin's face and instead the one we THINK is the Assassin was actually his last target who took over his identity.
The Matrix Revolutions: Mary Alice replaced Gloria Foster as The Oracle because the character's appearance had changed due to The Merovingian being given her "termination code". In reality, this was an ad hoc handwave made up by the writers because Gloria Foster had died.
Parodied in the animated film Bolt. When Penny decides to quit acting, the TV show she works for replaces her and explains her change in appearance as the result of reconstructive plastic surgery.
Parodied in the 2008 Get Smart movie. Agent 99 (Anne Hathaway) is shown to have undertaken extensive plastic surgery after her cover was blown. She used to look like a 40 year old blond woman. Now, she's a brunette in her mid-twenties.
Blofeld, arch-nemesis of James Bond is a villainous example. He was played by several actors over the years, with his changes of appearance being explained by plastic surgery. Somewhat justified in that if anyone has the money to be able to employ a magic plastic surgeon it's Blofeld.
Bond himself is generally not thought of as an example since the films don't explain his change in appearance. However, in the first movie where Bond's actor changed, the film begins with Bond being rejected by a woman. He then remarks "this never happened to the other fellow!" Some fans have taken this as evidence for the theory that "James Bond" is an alias passed from one 007 agent to the next.
The producers of On Her Majestys Secret Service did briefly consider the plastic surgery idea for Bond, but (wisely for the long run) dropped the idea.
The Gemini Killer in The Exorcist III. When he's seen from the main character's perspective, he's played by Jason Miller; when he's seen through what he calls the "eyes of faith", he's played by Brad Dourif.
Jobe Smith was played by Jeff Fahey in The Lawnmower Man and Matt Frewer in Lawnmower Man 2: Beyond Cyberspace. The clever rationale is that the explosion at the end of the first film badly burned him, and so he looked different after his face was reconstructed using skin grafts.
Less clever when, in the ending of the original film, Pierce Brosnan's character discovered that Jobe had completely uploaded himself into the mainframe, leaving only his skin behind in the real world.
Tomie from the live action adaptations of Junji Ito's comic of the same name is this. Due to cloning and regeneration no two Tomie's look alike.
Live Action TV
The Trope Namer is the Doctor in Doctor Who, as mentioned above. Each new regeneration brought with it a new characterization, costume, and personality. But, significantly, all memories and experiences of the past incarnations are maintained, along with a certain amount of character stability (he's always going to be quirky and altruistic and fight evil aliens), meaning the Eleventh Doctor is the exact same person as the First Doctor. Personality is a combination of "nature" and "nurture" - one story said that "Although the aspects of their personality caused by "nurture" would not change, the "nature" contribution to their personality would." The mechanic was implemented back when William Hartnell was playing the First Doctor, and obviously growing too ill to carry on further. A decision was made to let him retire and bring in Patrick Troughton for the role, and the writers decided that since the Doctor is an alien, he could change form into a new body if his current one was giving out. From there, the plot device has been modified into the go-to response for any actor wanting to depart from the role of the Doctor- kill off the current incarnation and regenerate him into the next actor, never invoking The Other Darrin.
The Doctor isn't the only Time Lord to get this treatment; The Master has had a number of onscreen incarnations, and Romana regenerated from Mary Tamm into Lalla Ward — who, confusingly enough, had appeared alongside Tamm in a serial just before she took over the role. This got explained by Romana liking Princess Astra's appearance so much she decided to regenerate into a double of her. A third Romana, played by Juliet Landau, was introduced in the EU audio dramas in 2013.
Borusa, a Time Lord on Gallifrey, was in a different regeneration (a different actor) in each of the four stories he appeared in.
This trope was also spoofed wonderfully in the unofficial 1999 Doctor Who comedy special "The Curse of Fatal Death," where the Doctor regenerates 4 times throughout the half-hour special. Particularly one moment where the Doctor uses up three bodies in less than a minute (including Hugh Grant's) all because he forgot to unplug a rather large deathray.
Though he's been shown to explicitly regenerate only once onscreen (two other times, he's just stolen bodies of other people), seven people have played the Master so far — Roger Delgado, Peter Pratt, Geoffrey Beevers, Anthony Ainley, Eric Roberts, Sir Derek Jacobi and John Simm. (Pratt and Beevers played the same regeneration in two different stories, making the Master a rare case of a character to have been both Nth Doctor and Other Darrin. This was made possible by heavy make-up, as in those two stories the Master was supposedly close to the end of his final life and had degenerated into a visibly decaying near-zombie).
A temporary case of this trope occurred in The Mind Robber. Fraser Hines got chicken-pox and had to be replaced for one episode by Hamish Wilson. Fortunately, that serial is something of a Mind Screw, so they were able to provide a "sensible" explanation: Jamie is reduced to a "puzzle" that the Doctor must solve by picking the right facial features. He does so incorrectly and gives Jamie the wrong face. Later on it happens again, and he is able to fix his mistake. Makes about as much sense as anything else that happens in that story.
Parodied in a sketch on End of Part One, where the Doctor gets zapped by a death ray, and reveals that it has gone straight through the copy of his contract that was in his jacket pocket. He then regenerates into a bug-eyed Tom Baker lookalike.
Yet another Time-Lord (or a part-Time-Lord, at least) has been shown to have the ability- the mysterious River Song aka Mels aka Melody Pond, daughter of Amy and Rory. This example of regeneration is particularly interesting for a number of reasons. 1) It's the first time that we meet a Time Lord's regenerations out of order (we begin with seeing River Song, then we see her first body as a child, and then that body as a baby, and then her second body from childhood to being a young adult. 2) She proved that the energy used in the regeneration can be used to heal others (a favour that the Doctor later reciprocated), so by the time of Forest Of The Dead her third body was already decidedly her final one.
The case of the Doctor is further complicated by the existence of versions of the Doctor that aren't "official" versions, most famously, the Valeyard from Trial of the Time Lord, who claimed to be a part of the Doctor from his own future. Also the Dream Lord from Amy's Choice, who was a psychic reflection of the Doctor's self-loathing...or something.
Again complicated a bit with the reveal that Paul McGann's incarnation regenerated into John Hurt's incarnation, making John Hurt's incarnation (credited as the War Doctor) the 9th incarnation and the 9th, 10th, and 11th Doctors the 10th, 11th, and 12th incarnations.
It was originally not (more) complicated. Because of how he ended the Last Great Time War neither he nor his successors considered him to actually be "The Doctor" so the Ninth Doctor was still the Ninth Doctor, just not the ninth face he's used. Of course, with "The Day of the Doctor", he redeems himself by changing history and regains the honor of calling himself Doctor...
Now made even more complicated. Turns out the Eleventh Doctor is the 13th incarnation, as the unaccounted for Regenerations were the War Doctor and the Metacrisis Doctor from The Stolen Earth. While this normally would mean he'd die as that incarnation, the Time Lords gave him a fresh batch of Regenerations in Time of the Doctor (long story), so he could regenerate a thirteenth time onto the "Twelfth" Doctor, who is actually the Thirteenth or Fourtheenth Doctor, depending on whether or not you're willing to count David Tennant as two separate Doctors.
To make things even more complicated (for newbies, anyway), due to the Doctor becoming technically a different person when he regenerates, on numerous occasions different incarnations have met and shared adventures, most recently in The Day of the Doctor then, technically all THIRTEEN known incarnations come together to save the day; and the Doctor later appears to meet a Fourteenth in the guise of an art gallery curator.
In a humorous policy trailer produced to accompany the theatrical release of The Day Of The Doctor for the show's 50th anniversary, Matt Smith appears as the 11th Doctor and claims he's just arrived after attending the program's 100th anniversary celebration, which featured "all fifty-seven Doctors".
K9's voice actor changed in season seventeen from John Leeson, the person most associated with the role (he's still voicing K9 to this day), to David Brierley. This was explained on-screen by K9 having "robot laryngitis" during the first story of season seventeen (and thus not having to speak or take part) and the Doctor not quite repairing him correctly until the next season.
In-verse, the Doctor left K-9 with companions who were parting company with him on a couple of occasions, unpacking a new copy of the robot dog for himself each time. (Presumably he downloaded the previous K-9's memories and personality into the new housing to ensure it remained "his" dog.) A heavily-modified version of K-9 also featured in the spinoff K9.
Spoofed in the Doctor Who 50th anniversary Google Doodle, a simple game about negotiating territory and running away from Daleks. Every time the player died, they regenerated into the next Doctor.
On the other hand, third-season Big Bad Rickman is replaced by a new actor after his first appearance, and this is explained as a side-effect of his vampiric medical condition: in his first appearance, his facial features change momentarily whenever he injects brain tissue from his victims. This transformation turns out to have a small but cumulative permanent effect as well. In reality, Roger Daltrey was simply too expensive to keep on as a recurring character.
On Mystery Science Theater 3000: Replacement of voice actors/puppeteers for the robots, as in most puppetry and animation, was usually unexplained. However, the difference in Tom Servo's voice from one actor to another was so severe, that it was given an on-screen nod as Joel replaced Servo's voice module. Similarly, in the eighth season Crow T. Robot was the only one who'd stayed on the satellite for five-hundred-odd years, and thus had gone slightly mad; any other vocal differences were given a Hand Wave in the tenth season when Joel (appearing as The Cameo) suggested that Crow had replaced the bowling pin that formed his mouth.
This was also lampshaded in episode 905, where Mike cut himself on Crow, becoming a Were-Crow. In giving Mike the rundown of what being Crow would entail, Crow mentioned that "your voice is gonna change inexplicably every seven years or so."
This was also joked about in an interview with Bill Corbett where he explained his initial lack of puppetry skills (as compared to Trace Beaulieu) by stating that "Crow had a stroke."
Star Trek: Deep Space Nine replaced Terry Farrell as Jadzia Dax with Nicole de Boer as Ezri Dax. It was already a well established part of the show's canon that the character of "Dax" was a symbiote that attached itself to a new humanoid host, thus explaining the new face and somewhat-different personality.
This replacement is also a partial Suspiciously Similar Substitute, since the show established that while the symbiote carried its memories from host to host, the hosts themselves were distinct individuals with their own personalities.
Interestingly, the episode "The Host" from Star Trek: The Next Generation plays this trope completely straight with regard to the Trill symbiotes; however, as a result it contradicts greatly with Deep Space Nine's portrayal.
The Borg Queen's hard to tell. She appears to be destroyed in almost every appearance - even by way of retcon, revealing herself to have been on the cube in The Best Of Both Worlds. Yes, her debut is an Unexplained Recovery. She's indicated and proven repeatedly that physical death is a minor inconvenience to her, and it's easy to imagine that her data just goes elsewhere when one body's in mortal danger, though that's not said outright. Coincidentally or not, she's sometimes Alice Krige and sometimes Susanna Thompson, and with so much make-up it's hard to tell who is who.
In Smallville, the recurring character Morgan Edge is initially played by Rutger Hauer, and after a near-fatal accident and Magic Plastic Surgery, he is played by Patrick Bergen, leading to this priceless quote:
Lex Luthor: You can change your face, your hair, your voice... but not your DNA. You still sweat the same.
In Series 1 and 2 of My Parents Are Aliens, Sophie Johnson was played by blonde Barbara Durkin. From Series 3 onwards, she was played by brown-haired Carla Mendonša, having 'got stuck' morphed that way.
Holly, the A.I. from Red Dwarf, became a female character at the end of series 2 and stayed female for the next three series, before later switching back to male.
Less noticeable was the recasting of the android Kryten (with Robert Llewellyn replacing David Ross, who originally was to return but was unavailable). This was mainly achieved when the look of the series was entirely redesigned, with a greatly improved budget allowing for better costumes and prosthetics, plus the fact that Kryten was only in one episode previously. Llewellyn played the part very differently, with this being explained in an Opening Scroll as Lister rebuilding him but being unable to restore his personality, this was further explored in Series VIII Episode 2 "Back in the Red: Part 2" when Kryten's behaviour is 'reset' and his actions and mannerism noticeable revert to the 'Ross' Kryten (before being restored to his old new self).
British children's comedy Mike And Angelo had Angelo - an alien - go through a regeneration process into another actor that was a direct reference to Doctor Who.
Inverted at the end of Season 1. Delenn uses an ancient machine to transform herself into a being with both human and Minbari characteristics, radically changing her appearance, but is still played by the same actress.
Babylon 5 also messed with the trope in a couple other ways. When the first actor to play Draal was unable to return due to illness, a new one was cast, the difference being remarked upon by Sheridan. Delenn replies that the Great Machine had restored to him his youth and appearance of thirty years prior. When the original actress to play Anna Sheridan was unavailable, they recast her with the real-life wife of the actor playing her onscreen husband, and although the backstory involved would have made it ridiculously easy to hand-wave the change in appearance, they instead played it as The Other Darrin. Fortunately, it was easy not to notice that it was a different actress.
Helped that they had a convenient replay of the only scene Anna Sheridan had been in, with the new actor instead of the old. JMS ALMOST did an Orwellian Retcon on DVD.
The characters migrate with actor availability as well... Carolyn Sykes becomes Catherine Sakai, becomes Anna Sheridan. JS becomes JS. Rather like the senior telepath/s and the second/s in command.
The death of Philip Gilbert shortly into Big Finish's The Tomorrow People line was framed by having TIM require some repair work after damage received in Gilbert's last episode. John had to rebuild TIM's voice synthesizer, and couldn't quite reproduce the original voice. Gilbert's other recurring roles (He also voiced a family of clones on whose voice TIM had been modeled) were not so lucky, and became Fake Shemps.
In Lexx, the change from Zev Bellringer to Xev Bellringer was explained via the former dying and melting into a puddle of goo, from which the latter was incarnated via the sacrifice of a few hapless astronauts. The reason given for her being so different in behavior and appearance after the resurrection is that the alien who brought her back was working from the imperfect memories of Zev's friends. It's worth noting that Xev still appears to have all of Zev's original memories, and is still part cluster-lizard due to Zev's botched love-slave transformation. Also, in a later episode Xev is briefly reverted to her original "ugly Zev" body, but later restored to Xev.
In Beetleborgs, Jo becomes the victim of a botched magical spell that alters her face from that of Shannon Chandler to that of Brittany Konarzewski. The change is permanent but a new spell makes everyone but the other heroes (and the viewer, of course) see her old face.
Subverted in a HUGE way by the Australian lifestyle show parody Life Support. In Season 3, Doctor Rudi changed actors, from Simon Van Der Stap to Jack Finsterer. However, it turned out that this new Dr Rudi, who had allegedly had Magic Plastic Surgery, was actually an impostor, and the old Dr Rudi was out for revenge. it culminated in a fist-fight between the Rudis at the new Dr Rudi and Sigourney's wedding.
On 'Allo 'Allo!, Herr Flick was played by Richard Gibson until series 9, when he was replaced by David Janson. To explain the change in actors (who looked NOTHING alike) Herr Flick had plastic surgery to radically alter his appearance so he would not be captured by Allied forces.
Used for numerous minor characters on Stargate SG-1, but this is an acceptable technique as the characters themselves are parasitic aliens (Goa'uld or Tok'ra) living in changable human hosts.
Used in Stargate Atlantis for Elizabeth Weir. Previously played by Torri Higginson, Weir returned first as a faceless, fuzzy-voiced Virtual Ghost, who then built herself a replicator body played by Michelle Morgan, who had in the previous season played F.R.A.N., a replicator McKay made. This allowed them to explain that to save time, Weir simply used the last template in the replicator machine, rather than try to remake her own appearance from scratch.
German 90's TV show Balko used this. After the first actor Jochen Horst playing the main character left, the next season started with a near fatal car accident, forcing the till then unseen character to undergo plastic surgery, turning him into new actor Bruno Eyron (among the possible new faces given to choose from was also a famous German shepherd dog, 'Kommisar Rex').
Supernatural: Demons can possess different human bodies, so any demon character can be played by more than one actor. It happened with Lilith in Season 3, and then with Ruby/"Kristy" between seasons 3 and 4.
It also occurred with villains Azazel and Alastair, and the possibility exists for this to happen with the angels as well. However, it's explicitly avoided with the character of Anna, whose human body was destroyed when she became an angel again, but replaced with an identical one as she'd become attached to it and and arranged for it to be remade.
The angels don't just switch bodies, they also don't care about the sex of their physical vessels. Castiel's alternative vessel was a 12 year old girl, Lucifer appeared as a woman in both Sam and Nick's dreams, and Raphael's second vessel was female. Fan theories vary on whether angels simply don't recognize gender in the way humans do or if they have a particular gender preference. But whatever you do, don't bring up the question of what this means for the hetero/homosexuality of ships involving angels.
Meg has also gone through several, including Sam's.
The Terminator known as Cromartie is reduced to a metal skeleton in the first episode of The Sarah Connor Chronicles, and slowly creates a new flesh covering for himself over the course of the first season, being played by a second actor in the interim stages, and a third actor once the work is complete.
Trance from Andromeda is interesting in that it was to change her makeup design instead of her actress. Part way through season two she's replaced with a future version of herself who looks completely different (even having a different skin colour), but she's still the same actress behind the makeup.
She still does act fairly differently however (presumably due to her being older and more mature than her previous self).
Indeed, the change is so convincing, and done in such a way that is seems like a straight-up example of the trope, you really have to go over the credits to convince yourself it's the same actress!
Shapeshifter Candice's favourite form was originally played by Missy Peregrym, but in her brief appearance in season 2 she had decided to change identities, and her new preferred form was Rachel Kimsey.
One of the most infamous (and convoluted) versions of this occurred on Days of Our Lives: When Wayne Northrop - the actor portraying Roman Brady - left the show in 1984, his character was Put on a Bus via shooting/body snatching. Two years later, the younger, taller Drake Hogestyn took over the role. Playing this trope straight, they explained his physical differences by plastic surgery needed to recover from the injuries suffered at the hands of Stefano DiMera. Then Northrop returned four years after that... as Roman Brady. He'd been held prisoner by Di Mera, while Di Mera sent brainwashed mercenary John Black (who, in an extra dash of Soap Operaness, turned out to be Stefano's half-brother) to take over Roman's life and be his spy (That didn't work so well for Stefano). But Northrop only stuck around three more years before leaving again. This time they went straight The Other Darrin and brought in Josh Taylor to play Roman (and has since 1997).
Parodied on Friends (and crossing over with The Bus Came Back) where Days of Our Lives exists as a Show Within a Show when Joey is brought back to the show by having his character (who had been in a coma for 5 years) receive a brain transplant from a female character who was being killed off. Dr. Drake Ramoray was back, but with Jessica Lockhart's mind.
Villain Al Hawke returns to Birds of Prey played by a different actor, his new face is explicitly the result of Magic Plastic Surgery to erase the scars of his burns from a previous episode. Unlike other examples, this doesn't explain why his personality, height, etc. all change between appearances, but hey.
Played with in Dollhouse. Many of the 'characters' are, or become, artificial constructs (imprints) that can be moved from body to body. Multiple actors interpret Topher, Dominic, 'Taffy', Dr. Saunders, Clyde Randolf, 'Kiki', Margaret, the serial killer in 'Belle Chose', and Caroline in this way. Generally as much as possible is done to retain the voice and mannerisms of the original, with the exceptions of Clyde and Dr. Saunders, who change and evolve as they go along.
In particular, Victor was imprinted with Topher enough times to count as a recurring character.
In the post-apocalyptic episodes, Ambrose and Harding are played by different actors than normal, explaining that they now jump bodies ("getting a new suit") regularly and have multiple copies of each other. The same thing was done to Rossum founder Clyde when Rossum was first starting.
Alpha 6's voice chip was damaged when the Power Chamber was destroyed at the end of Power Rangers Turbo, necessitating a repair that gave it a new personality, a new voice and familiar mannerisms, also explaining away the voice actor switch from Katerina Luciani to Wendee Lee. Alpha 6 would get Other Darrined without explanation in Power Rangers Operation Overdrive, where it is voiced by New Zealand-based American actor Campbell Cooley with a voice that sounded a lot more like Alpha 5.
In the The Adventures of Superboy TV series Lex Luthor was Nth Doctored through plastic surgery while Superboy himself was Other Darrined.
In the Disney sitcom Wizards of Waverly Place. Max is struck with a spell that turns him into a little girl and is replaced by said actress for five episodes until they managed to reverse the spell.
At the conclusion of the 10th season of Dallas, Victoria Principal chose to leave the series and as a result her character Pam was severely burned in a tanker explosion. Pam later reappeared in one episode two seasons later, now played by Margaret Michaels, with some plastic surgery to explain the change in appearance.
Used as a major gameplay mechanic in the Doctor Whopinball game: The Master has effectively trapped six of the (then) seven Doctors in different places, and the Seventh must get them to safety in order to confront The Master, the Daleks, and ultimately Davros.
To replace the late Peter Jones in the Tertiary Phase of The Hitchhiker's Guide to the Galaxy, the guide receives an "update" during the first scene of the play. Thanks to some clever editing, the voice of the Guide changes in mid-sentence, and occasionally reverts back for a second, using recycled audio from the original series.
The first actor to play The Lone Ranger on the radio died tragically in a car crash. To further a) a seamless transition of the character and b) to keep young viewers from being freaked out by the Ranger's sudden vocal change, the producers decided to have the Ranger be struck mute for a few episodes before introducing the new voice of the Ranger, Brace Beemer.
In Dragon Age, aside from still being voiced by Kate Mulgrew, Flemeth's valkyrie-esque appearance in the sequel is radically different from her old hag appearance in the first game. Justified as she's a Voluntary Shapeshifter capable of adopting A Form You Are Comfortable With, as well as being able to possess people to prolong her life. However, a third possibility that she points out to Hawke, is whether or not her true form is even human anyway?
Hawke: Impressive, where did you learn how to turn into a Dragon? Flemeth: [Laughs] Perhaps I am a Dragon?
Eddsworld: Edd got zapped by a voice changer at the start of Space Face Part 2 to justify his VA's change, which happened due to Edd Gould's death. The character is now voiced by Tim Hautekeit.
TimelordBlog: As the character appearing in the blog is the Doctor him/herself, the character goes through a regeneration whenever the Mun gets tired of that specific Doctor. So far, we've had twelve (Dave Strider), thirteen (Ritsu Tainaka), and fourteen (Mami Tomoe).
In Roommates, because it's a Mega Crossover and has a whole cast of Living Dreams, when a different adaptation of the source material becomes more well known the powers of the universenote Namely Clap Your Hands If You Believe and Actor Allusion change the appearance of the characters. It's generally not permanent, though, as they are Composite Characters and by definition encompass all their portrayals. (They possess a very limited shapeshiftingnote They must remain the same character and probably the version can't be too obscure either. ability thanks to this too.)
Autobots and Decepticons in Transformers often upgrade, and occasionally mutate, into newer, more powerful bodies. While generally a way to advertise new toys, this is occasionally (though not usually) used to justify new voice actors: when Megatron was rebuilt as Galvatron in the animated movie his voice changed from Frank Welker to Leonard Nimoy (Galvatron in the series proper was still voiced by Frank Welker, though). Also, Scourge and Cyclonus had new voice actors instead of those of Thundercracker and... either of the two characters Cyclonus could be. (Long story.) Beast Machines Jetstorm has a different voice than Silverbolt, because it'd ruin the surprise.
Retro-actively applied in Reboot: at the end of season two Bob is sucked into the Web, and when he came back in season three, slightly degraded by his experience, he switched voice actor from Michael Benyaer to Ian James Corlett because the former was unavailable. When Benyaer became available again while producing season four they had him do the voice for Bob in a flashback, a second Bob (possibly the original, possibly a copy, actually Megabyte), and the real Bob after the damage done to him by the Web is repaired, implying the different voice was caused by said degradation.
Count Duckula: A few episodes revolved around the fact that Duckula's ancestors were actually him, and he just comes back slightly different every time he is resurrected. The latest incarnation is just particularly unique due to a mishap in the resurrection ritual (they accidentally used ketchup instead of blood).
In The Simpsons, it's suggested that Duffman is actually a series of actors playing the role, after Homer mentions having thought he'd heard that he'd died some time ago.
Duffman: Duffman can't die, only the actors who play him. Oh yeah!