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->''"In the heat of composition I find that I have inadvertently allowed myself to assume the form of a large centipede. I am accordingly dictating the rest to my secretary."''
-->-- A letter from '''Screwtape''', ''Literature/TheScrewtapeLetters''

A character possesses some manner of ShapeShifting ability, but not the conscious ability to control when this ability kicks in.

This isn't necessarily as bad as it sounds -- explanations are usually one of the following:

* Sometimes this is the normal rule of their personal shapeshifting -- shapeshifting ''does'' come in a wide variety of types, after all. Natural examples of this include {{Empathic Shapeshifter}}s, [[OurWerewolvesAreDifferent certain breeds of werewolf]], and characters HulkingOut.
* Sometimes it's the result of PhlebotinumBreakdown applied to an otherwise {{Voluntary Shapeshift|ing}}er -- maybe their TransformationTrinket is malfunctioning, they're a victim of a DemonicPossession, have a SplitPersonality, or are in the middle of a [[ShapeshifterIdentityCrisis midlife identity crisis]] (in which cases you're more likely to see [[TheMindIsAPlaythingOfTheBody their personality transform as they do]]). Or maybe they've received a mortal blow and their ability [[ShapeshifterSwanSong goes haywire as their life flickers out]]. If they're not in danger of dying, they usually just need a [[SneezeOfDoom good allergy pill.]]
* Conversely to the above, if a character has just recently obtained a shapeshifting license, maybe they just [[HowDoIShotWeb don't know how to operate it yet]] (phlebotinum doesn't always come with instruction manuals, you know). If this is the case, expect it to be the focus of one or two chapters/episodes until they get the ability under complete control.

In any case, the character is generally aware they have this ability, and it's a recurring aspect of their character; the shapeshifter will generally try to avoid triggering their ability accidentally (e.g. [[ComicBook/TheIncredibleHulk Bruce Banner]] constantly warning people YouWouldntLikeMeWhenImAngry); alternately, they can expose themselves to the trigger to deliberately invoke their ability when it's convenient (e.g. stimulus + container to hide it = instant TransformationTrinket); the line between voluntary and involuntary can get a little blurry, but unlike the Voluntary Shapeshifter, the involuntary one lives with a risk of transforming [[FinaglesLaw at the most inconvenient moments]] should their trigger hit them unexpectedly. (Even if they don't end up transforming very often, the potential for it is still there.)

Not to be confused with just any 'involuntary shapeshifting' in general, like the BalefulPolymorph (a popular source of many unexpected, involuntary transformations) or a FisherKingdom (where the shapeshifting power is a trait of the kingdom itself, not the person).

Frequently overlaps with {{Animorphism}} since animals are a popular choice for shapeshifting (both voluntary and otherwise) already.



[[folder: Anime and Manga]]
* The title parasite-implanted-within-character from manga and one-shot 1989 OVA ''Baoh: The Visitor''. Less a true shapeshifter than a being with amazing transformative abilities. While the protagonist, Ikurou Hashizawa, certainly won't be winning any points for his looks any time soon (at least in his transformed state; in his OrdinaryHighSchoolStudent persona, he's not nearly so hideous) he ''is'' outfitted with a [[NewPowersAsThePlotDemands veritable arsenal]] of [[ShapeshifterWeapon biological weapons]] and is nigh-indestructible. And perhaps most importantly, he seems to retain most if not all of his awareness and reasoning abilities even when transformed.
* ''Manga/UruseiYatsura'' has Rei, [[GreenSkinnedSpaceBabe the green-haired space bishonen]] [[ChickMagnet 99.9% of the female cast lusts after at one point]]...and his anger (jealousy)/excitement (food) - triggered transformation. Has to be seen to be believed.
* ''Manga/RanmaOneHalf'': Ranma, Genma, and all the other Jusenkyo-cursed characters. This sometimes borders VoluntaryShapeshifting as hot and cold water are something that can be obtained fairly easily...but are also hard to avoid.
* Several members of the Sohma family in ''Manga/FruitsBasket'', due to a curse that makes them turn into an animal from the Chinese zodiac whenever they're hugged by someone of the opposite sex or physically weakened. The cat has a second, monstrous form and must wear prayer beads to appear human.
* On ''Manga/TokyoMewMew'', Ichigo's cat ears and tail pop out whenever she's frightened or excited. This occurs most often in the presence of her love interest, but also inadvertently led to the discovery of the fourth Mew Mew. This later intensifies as she [[{{Animorphism}} becomes an actual kitten]].
* In the ''Anime/RevolutionaryGirlUtena'' movie, Utena and Shiori turn into cars, for reasons that only make sense if you read the plot as an [[MindScrew allegory]]. Nanami also turns into a cow (or at least [[MindScrew thinks she does]]) in both the regular series and the movie.
* ''Anime/PrincessTutu'': Princess Kraehe's TransformationSequence; her SecretIdentity tries to deny Kraehe's existence, which only seems to increase her hold on the body. Tutu's own transformation might be considered involuntary, too, as the behind-the-scenes author that "writes fate" at the beginning of the story calls her into being by speaking her name; however, she always agrees to it. What Ahiru ''doesn't'' agree to, though, is turning into a duck when she gets excited and having to cart her clothes to the nearest water source.
* Young mermaids in ''Manga/MyBrideIsAMermaid'' transform if splashed with water, making a water gun a viable weapon on one occasion. With enough practice and focus, one can (painfully) resist this effect.
* ''Manga/DragonBall'' character Lunch (Launch in the American dub) changed personalities (and hairstyles) whenever she sneezed. The Oozaru, or "great ape" transformation on the full moon is essentially this for all Saiyans. The only way to stop an Oozaru rampage is to chop off the Saiyan's tail or blow up the moon. For Goku and Gohan, it's very much a curse, though other, more bloodthirsty Saiyans (such as pre-Namek Vegeta) use the transformation to their full advantage. This of course has something to do with the fact that they are apparently able to keep their minds while transformed and direct the brute power. Goku becomes fully animalistic while transformed with no memory of his actions in Oozaru form afterwards, [[spoiler: making him unaware that it was he who killed his grandfather.]]
* In Akira Toriyama's work ''Manga/DoctorSlump'', Chinese immigrant Tsun Tsuku-tsun inexplicably turns into a tiger when he comes into contact with a girl.
* ''VisualNovel/{{Kanon}}'' has an animal to human one in [[spoiler:Makoto]].
** Which gets revisited in ''VisualNovel/{{Clannad}}'' with [[spoiler:Shima]], with all the [[TearJerker Tear Jerking]] drama that comes with it.
* [[LiteralSplitPersonality Ren/Run]] in ''Manga/ToLoveRu''. Ren transforms into Run (his female self) and back whenever he sneezes. Each of them has his/her own mind and can communicate with each other, but Run loves Rito and Ren loves Lala. Although Ren usually transforms because of an unexpected sneeze, Run tends to [[PepperSneeze force]] herself to sneeze when one of her plans (usually to embarrass Lala in front of everyone) fails, making it a not-so-InvoluntaryShapeshifting.
* Much of the initial storyline of the manhwa ''Manhwa/TheBrideOfTheWaterGod'' is moved by the fact that [[spoiler:the eponymous Water God Habaek becomes a little boy during the day and only regains his true adult form at night]].
* [[spoiler:Negi]] of ''Manga/MahouSenseiNegima'' [[spoiler:has been in the process of [[PainfulTransformation transforming]] into a demon ever since he started using [[BlackMagic magia Erebea]]]]; this transformation manifests if he loses control of his emotions. Once he found out, he decided that instead of trying to stop it, he should just complete the transformation and get it over with immediately.
* In ''Anime/TheCatReturns'', the FisherKingdom effect of the cat's world lingers on protagonist Haru; even after returning home, she still turns into a CatGirl whenever she's around the Baron.
* This is done several times in ''Manga/{{Pokemon}}''. Castform changes shape depending on the weather. In the Manga/PokemonSpecial manga, Red's Eevee would "Evolve" every time he got near a Thunder, Fire, or Water stone, as a result of some genetic experimentation performed on him by Team Rocket. (This stopped when he permanently evolved into an Espeon.) Also, Deoxys can change shape depending on what region it's in. In the manga, Team Rocket managed to find a way to emulate other regions so Deoxys could transform voluntarily. However, during a battle in Kanto, the stones that allowed it to transform into its Hoenn forms were destroyed while Deoxys was in its Hoenn form, which hurt Deoxys badly.
* ''WesternAnimation/SabansAdventuresOfTheLittleMermaid'' sees the title character able to use a magic whistle to switch forms between human and mermaid, but she will revert back to a mermaid whenever she gets wet. Cue the villains constantly dumping things on her at the most inopportune moments.
* Protagonist Kate Menella from ''Manga/LoveIsInTheBag'' turns into a bag whenever she gets excited over something.
* The five protagonists in ''Manga/AmeNochiHare'' will transform into girls whenever it rains.
* Yayori from ''Manga/NekoDeGomen'' has little control over when she has [[CatGirl cat ears and tail]] and when she doesn't.
* ''The Face Burglar'', like all of Creator/JunjiIto's works, takes this trope and dives headfirst into a pool of NightmareFuel with it. Kamei is a high-school student that, with enough contact with someone, will eventually assume their form. Eventually the students all don ''Youkai'' masks and surround her, taunting her while she screams in pain and mutates. [[BodyHorror The end result is not pretty.]]
* In ''Manga/TheSevenDeadlySins'', King, a fairy, sometimes shape shifts into his [[{{Gonk}} human form]] as a form of his expression in any given situation.
* This also applies to the half-demon Izumo/Gyu-oh to from the anime ''Manga/{{Inuyasha}}''. During the day he looks like a pure human, but at night he looks like a pure demon.
* Inukai from ''Manga/FlyingWitch'', after getting drunk and eating some magic chocolates, turns into an anthropomorphic dog during the day against her will. At night, she returns to human form.

[[folder: Comic Books]]
* [[Creator/MarvelComics Marvel's]] [[ComicBook/TheIncredibleHulk Bruce Banner]] is the poster child (and TropeNamer) for HulkingOut, due to his transformations being involuntarily triggered by anger or stress. At a couple of different points he becomes more stable, either locked into a particular form for a stretch or able to take control over his emotions to the point that he can mostly suppress or evoke the change as desired.
* ComicBook/SpiderMan is at times forced to battle The Lizard, a scientist and friend who periodically transforms into a [[LizardFolk lizard-like humanoid]] by way of the [[HealingFactor experimental regenerative treatment]] he tested on himself, usually triggered by extreme stress. In addition, Spidey himself has had trouble with more spider-like mutations.
* Comicbook/GhostRider used to transform at night. After a while, he would transform whenever there was danger nearby, regardless of the time of day. But eventually, he became able able to control it completely.
* In ''ComicBook/BatmanGothamAdventures'' #58, ComicBook/TheCreeper (Jack Ryder, who in the Franchise/{{DCAU}} was transformed into the Creeper by Joker's laughing gas and toxic waste) is seen involuntarily transforming due to not using the medicine and a bit later mentioning that Creeper has gotten stronger and now only needs a rush of adrenaline to transform even under the medicine. (So he jumps out of the apartment building's window.)
* The now-discontinued Marvel/DC universe character Man-Bat suffers from this at first. He is a scientist who so admires Batman's efforts to stop crime that the scientist tries to give himself bat-like powers so he can emulate Batman. He ends up randomly transforming from human to half-bat form for much of his career, until he discovers drugs which let him control his transformations.
* A ''Franchise/DonaldDuck'' comic story by Carl Barks once used a variation where Magica De Spell comes up with a concoction that, after having been sprayed onto somebody's face, would change the victim's face to that of anyone they look at. She naturally plans to use it to blackmail Scrooge to get his dime.
* In ''ComicBook/CaptainBritain'' Meggan is capable of transforming in a controlled fashion, but her shapeshifting powers are also linked to her [[TheEmpath empathic powers]] and can cause her to transform based on how others perceive her. Early in life the fear local villagers had of her caused her to take on a more monstrous form, resulting in them fearing her more, and so on. Her "[[ShapeShifterDefaultForm default]]" elf-like form is actually based on what her long-term boyfriend finds attractive.

* The T-1000 from ''Film/Terminator2JudgmentDay'' suffers this after recovering from being frozen and shattered in the foundry. It's a series of deleted cutscenes showing the cyborg keep losing control of his colours and changing to the environment that he walks on.
* Occurs in just about every incarnation of ''Film/TheShaggyDog''.
* Madison in ''Film/{{Splash}}'' turns back into a mermaid whenever she gets wet, as demonstrated in the scene where the mad scientist Walter sprays her with a hose.
* ''Film/TheNuttyProfessor'': Quite a lot happens in the '90s remake, especially at the end.
* ''Film/{{Ladyhawke}}'', a story of two lovers. By day, she is a hawk. By night, he is a black wolf. And as long as a [[NoManOfWomanBorn day is followed by night and a night is followed by day]], they can never meet.
* In ''Beyond Sherwood Forest'', Alina turns into a dragon whenever sunlight falls on her, then she reverts when she is in the dark.
* In ''Film/TheWolfman2010'', much as he would like to, Lawrence is unable to stop himself from transforming and is completely subject to the phases of the moon.
* In ''Film/{{Zelig}}'', the titular character played by Creator/WoodyAllen is discovered to have this ability and called "The Human Chameleon". The reason for this is not because of any magic, but due to his psychology that stemmed from not being able to admit he read ''Moby-Dick''. This resulted in him being so desperate to fit in that he changes opinions, facial hair, race, but not genders.

* ''Literature/TheScrewtapeLetters'', by Creator/CSLewis, provides the page quote. In a letter to his idiot apprentice Wormwood, the titular bureaucrat devil Screwtape works himself up to so much anger that he accidentally transforms into a giant centipede.
* In ''Literature/{{Animorphs}}'', Rachel has an allergic reaction to a crocodile morph, and the book "The Reaction" deals with her uncontrollable changes back and forth. One book has Marco changing into hybrid morphs whenever he is stressed out. At the worst possible times. And some of them, like the Osprey/Lobster, couldn't even ''breathe.''
* From Creator/TerryPratchett's Literature/{{Discworld}} series:
** In ''Discworld/WitchesAbroad'' Nanny Ogg's cat, Greebo, is temporarily turned human. As seen in ''Discworld/{{Maskerade}}'', his morphic field remembers the shape and shifts back to it when under stress, much to Greebo's consternation.
** In ''Discworld/TheLastContinent'', the Librarian catches the flu and, again, because of a weakened morphic field, changes shape every time he sneezes.
** Werewolves ''have'' to transform in the light of the full moon, but beyond that they can change whenever they like. There's a variant in Lupine from ''Discworld/ReaperMan'', a wolf who transforms into a ''human'' at the full moon.
* In Katie [=MacAlister's=] Aisling-Grey-Series, Drake (Aisling's mate and dragon-in-human-form) shapeshifts only when he orgasms, otherwise he isn't able to willingly shapeshift anymore.
* Sewer Jack of the ''Literature/WildCards'' series turns into a huge alligator under stress. His life has a ''lot'' of stress.
* If you're in ''Series/TheDresdenFiles'', there's a couple choices for shapeshifting. There's regular VoluntaryShapeshifting, which the Alphas and [[spoiler: Injun Joe]] know. There's some nifty BlackMagic belts that turn you into a wolf (and corrupt your soul), and then there's ''loup-garous''. As in, NighInvulnerable [[TheBerserker Berserker]] [[OurWerewolvesAreDifferent Super-Werewolves]] that change every lunar cycle no matter what and need the type of power that could restrain ''an archangel'' to hold them. There's a reason that all Harry has to do to communicate to Murphy in a later book that the police can't help with the problem they're dealing with is to say it's 'worse than the loup-garou'.
* In Marie de France's ''lai'' ''Literature/{{Bisclavret}}'', Bisclavret must change into a wolf every week, and can not change back without his clothing.
* In the ChivalricRomance ''The Swan Children'', the children are born (to a [[ShapeshiftingLover swan maiden]]) with chains about their necks. When these are removed, they turn into swans.
%% * As werewolves, Wolfs of course transform at the full moon. However, if they become too distressed they will also transform then, which is a very painful process. [[spoiler:The strain of it plus injuries sustained kills Wolf.]]
* In JK Rowling's ''Literature/HarryPotter'' books, involuntary shapeshifting at the full moon is [[OurWerewolvesAreDifferent part and parcel of lycanthropy]]. It cannot be cured, but a Wolfsbane potion can be used to counteract TheMindIsAPlaythingOfTheBody. Boggarts ''are'' capable of voluntary shape-shifting (which they use to become something frightening), but the spell used to counter these creatures causes them to involuntarily shape shift into something funny.
* Played for laughs in Thorne Smith's screwball comedy novel ''The Stray Lamb'' (1929): T. Lawrence Lamb meets a little russet man who puts a spell on him that causes him to transform into different animals uncontrollably - first a horse, but also a seagull, a goldfish, a cat, a lion, a dog and a kangaroo.
* A ''Series/{{Torchwood}}'' spinoff novel reveals that this has happened to Torchwood employees so often in the past that they provide an informative pamphlet on what to do (last updated 1958). It notes that if you're capable of ''reading'' the pamphlet, you've already passed the biggest hurdle by not going utterly [[GoMadFromTheRevelation mad from the revelation]] or dying from incompatibility of nervous systems.
* In Creator/DevonMonk's ''Literature/DeadIron'', Cedar's werewolfery is this. As opposed to the BalefulPolymorph his brother got.
* In Creator/SarahAHoyt's ''Literature/DrawOneInTheDark'', both Tom and Kyrie shift under the influence of emotions and the moon. [[CommonalityConnection A bond between them.]]
* In Creator/RuthFrancesLong's ''Literature/TheTreacheryOfBeautifulThings'', [[spoiler:Jack]] turns into the [[spoiler:green man]] every night.
* At the end of ''Literature/{{Awakened}}'', [[spoiler:Rephaim is given a human form by Nyx, but he must become a raven again during the day]].
* In Creator/SusanDexter's ''The True Knight'', Savrin, pushed into the river, turns into an otter until a wizard catches her and pulls her out, whereupon she turns back. Later, he pushes her in again to save her, and she turns to an otter again, and nearly drowns in her clothes. When Titch rescues her, she turns to a duck and then a salmon, trying to escape, but remembers nothing after.
* In ''The Particular Sadness of Lemon Cake'' by Aimee Bender, the protagonist (who herself has the ability to taste emotions) Rose's brother Joseph disappears into thin air throughout the novel, at one point right before his high school graduation. [[spoiler: Near the end of the book it is revealed that he involuntarily turns into pieces of furniture for varying periods of time. At one point, he simply turns into a chair and never turns back.]]
* The werewolves from ''Literature/WolvesOfMercyFallsSeries''. Shifting all depends on the temperature. How cold it needs to be for a werewolf to shift from human to wolf depends.
* In ''Literature/TheGirlFromTheMiraclesDistrict'', Nikita's berserk form is triggered by high adrenaline levels. She has a spinal implant that helps keep them in check, but it's far from a perfect solution.
* ''Literature/TheCrimsonShadow'': Greensparrow made a pact with a dragon to share his body in return for magical powers. Most of the time he can control this, but the dragon forces him to transform occasionally.
* In the ''Literature/SonjaBlue'' series, people who become vampires experience some moderate involuntary shapeshifting when they first transform. Not a lot, but enough to hide their previous identity. (It conveniently includes fingerprints.) This is why nobody knows that Blue is actually the long-lost heiress Denise Thorne.

[[folder: Live Action TV]]
* ''Series/{{Galidor}}'': The main character's special ability allows him to exchange his limbs with other beings, an ability which works properly a very small percentage of the time.
* The British TV show ''Series/{{Woof}}!'' is based around the premise of the main character unexpectedly turning into a dog at the most inconvenient moments, with the only warning being a suddenly itchy nose.
* ''Series/StarTrekDeepSpaceNine'': Odo's race, the Changelings, cannot maintain solid forms for extended periods of time, with Odo himself having to occasionally return to his native liquid form, usually once per day. His main piece of furniture? A bucket to sleep in. In one later season, Odo is [[ShapeshifterModeLock locked into]] his [[HumanityEnsues humanoid form]] as a punishment for being the only Changeling to kill another Changeling. He got better. In another he's the victim of a device that prevents him from shapeshifting while it's active, as a form of torture. What happens to him isn't pretty. In "The Alternate" episode, he unconsciously transforms into a monster several times after being exposed to a strange gas on an alien planet.
* ''Series/FraggleRock'' gives us Skinfred, a one-off EmpathicShapeshifter whose physical appearance changes depending on ''what other people think about him''; it's impressive how upbeat his personality is given this form of being BlessedWithSuck. Red and Wembly like him, think he's very cute and friendly...and that he sports goofy pigtails. Ma Gorge does ''not'' like him, thinks he's creepy and scary for living in her flooded basement, and wonders if he's actually a giant, fanged, two-headed monster. [[ClapYourHandsIfYouBelieve Guess what happens next.]] (Skinfred: "Aw, I '''hate''' having to be a monster!")
* ''Julia Jekyll and Harriet Hyde'' has this as the theme, the main character is a girl who uncontrollably turns into a furry yeti-like thing at inopportune moments.
* ''Series/H2OJustAddWater'': The mermaid girls change forms when in contact with water.
* In one episode of ''Series/MysteryScienceTheater3000'', "The Undead", a witch named Lydia (who transforms into a bat in the movie), appears on the Satellite of Love. As she tries to deliver a scary speech to Mike and the 'Bots, she starts shapeshifting into all sorts of things, uncontrollably. "I've never been a football before!" She ends the segment [[AndIMustScream stuck]] as a bottle of drain cleaner. The funniest one is when she very briefly shifts into Pearl Forrester, who looks very confused at her new surroundings.
* ''Series/DoctorWho'': Time Lords can "regenerate" when dying, an EmergencyTransformation that revives their body with a new life (and a [[TheNthDoctor new actor]]). It is unclear whether or not the regeneration process is voluntary or if it happens automatically; in one episode, the Master voluntarily refused to regenerate, choosing to let himself die. Also, regeneration does not seem to be a particularly traumatic experience in Time Lord society, with its members casually congratulating each other on their new appearance. It's only the Doctor who seems to have a particularly tough time of it.
** Saibra from ''[[Recap/DoctorWhoS34E5TimeHeist Time Heist]]'' assumes the appearance of anyone she touches, for as long as they remain touching. She can choose to retain the appearance for as long she likes after they stop touching, but she can't choose not to mimic a person while they're in contact.
* In the first episode of ''Series/{{Angel}},'' the title character immediately guesses that Doyle is a demon. He insists that he's not--then sneezes, causing numerous spines to come out of his face. "[[HumanMomNonhumanDad On my mother's side]]."
* ''Series/{{Charmed}}'' had an episode almost exactly like the ''Film/{{Ladyhawke}}'' one above, except with an owl instead of a hawk and the genders/animals switched. And of course, it becomes a RunningGag how often one or more of the girls are transformed into a demon/vampire/genie/wood nymph/Fury/Valkyrie/etc.
* ''Series/TheMagicians2016'': Kady, Penny, Quentin and Alice turn into geese at the end of their test, flying to Antarctica in that form. Later Quentin and Alice become foxes in Antarctica-they even have sex that way.
* ''Series/LegendOfTheSeeker'': The king in "Cursed" turns into a monster by night to stop the D'Harans invading. He can't stop it, even killing his wife unknowingly. [[spoiler: After he dies, his daughter receives the curse.]]

[[folder: Mythology and Folklore]]
* In European folklore, there are two kinds of werewolves - the merely cursed and the truly evil. Those cursed are not in control of their shapeshifting; it being an artifact of phases of the moon and/or the presence of certain plants (such as "Wolfsbane", aka ''Aconitum'' spp.). The latter ''deliberately'' turn themselves with evil witchcraft, which typically involves wearing fur of a wolf on their back.

[[folder: Newspaper Comics]]
* In ''ComicStrip/SafeHavens'' it is established that although [[OurMermaidsAreDifferent mermaids]] can [[VoluntaryShapeshifting generally shapeshift freely]] between mermaid, fish, and human forms, if a mermaid remains in human form for 12 hours they must spend their next 12 hours as a fish (and vice versa) to balance it out. This is a plot point for the mermaid Remora after she joins the (otherwise human) regular cast; in one event her personal {{Masquerade}} is nearly discovered when a basketball game runs into overtime and the team has to get her off the court before her transformation kicks in.

[[folder: Tabletop Games]]
* In ''TabletopGame/DungeonsAndDragons'', afflicted lycanthropes (those who were bitten, rather than having been born with the condition) do not have perfect control over their shapeshifting, and may involuntarily assume their alternate forms in response to damage or the full moon.
* The Tau's Kroot minions in ''TabletopGame/Warhammer40000'' assimilate the properties of whatever they eat, whether they want to or not. This means that all Kroot must eat sentient creatures or devolve into beasts themselves.
* ''TabletopGame/MagicTheGathering'': Changelings are every creature type at once. This includes anything from squirrels, whales, to Gods. That being said, they are affected by anything targeting a specific kind of creature, be it beneficial or downright fatal. A typical [[HordeOfAlienLocusts Sliver]] does not itself possess the ability to shapeshift (except if that ''is'' its ability). Their shifty-ness comes from the fact that they tend to share their inherent abilities with other Slivers. If said ability is having, say, an extra arm, a pair of wings, or even a second freakin' HEAD, that ability is passed to any Slivers nearby, be they allies, neutral, or hostile. The shared ability is also lost when the source Sliver either leaves the area or dies. In a single battle one may encounter Slivers spontaneously sprouting and losing all manner of appendages and protrusions. This power is (was) completely beyond their control. Que a bit of FridgeHorror for them when one considers how bad growing pains can be; imagine having an extra limb suddenly pop out from your chest within seconds, complete with the sound of snapping tendons and straining muscle.

[[folder: Video Games]]
* ''VideoGame/KingdomHearts'': Due to a HeroicSacrifice from the first game, when Sora transforms into his [[SuperMode "Drive" forms]], it may occasionally "malfunction" and turn him into "Anti-Sora" (who looks very similar to a Heartless) instead in ''VideoGame/KingdomHeartsII''. Riku transforms into [[spoiler:Xehanort's Heartless]] to tap into his power. He regains his normal form because [[spoiler:exploding]] Kingdom Hearts' power 'purified' him of the foreign influence.
* Vincent Valentine of ''VideoGame/FinalFantasyVII'' has this problem thanks to Hojo. He has [[LimitBreak varying degrees of control]] over it, although in ''Dirge of Cerberus'', he can't control his Chaos transformation [[spoiler: when the Protomateria is pulled out of his body.]]
* ''VideoGame/OsuTatakaeOuendan'': Goro Okami wolfs out at the sight of round objects (be it a bald head, eggs, a baseball, ear rings and eyes). He fears that this will freak out her date but in the end, [[spoiler:she finds out and loves him even more.]]
* ''VideoGame/CaveStory'': During the closing credits, [[spoiler:Sue and Itoh are returned to their human forms, only to revert back to their Mimiga forms when they sneeze. Whether or not this becomes a recurring problem is never explained.]]
* Certain Franchise/{{Pokemon}} in the videogames have the ability to change between various physical forms. The third-generation Pokémon "Castform", for example, changes its shape (and elemental type) depending on the current weather. (Castform also has the ability to control the weather.) Giratina can only assume its serpentine Origin Form with the help of the Griseous Orb, and Shaymin can only transform into its Sky Form with a Gracidea flower in its possession.
* In ''VideoGame/PrinceOfPersiaTheTwoThrones'', the Prince acquires a "Dark Self" that takes over his body during times of extreme danger (though the player is still in control of the Prince), and can only change back if he touches water.
* ''Franchise/TheElderScrolls''
** In every game starting with ''[[VideoGame/TheElderScrollsIIDaggerfall Daggerfall]]'', the PlayerCharacter can catch one of the [[ViralTransformation diseases which leads to vampirism]] and then undergo this to become a [[OurVampiresAreDifferent Vampire]]. After this happens, you risk damage (or at least weakness) from sunlight and, depending on the specific vampire bloodline, either magically drain health from [=NPCs=] or [[BreakingAndBloodsucking drink blood from sleeping]] [=NPCs=]. In ''[[VideoGame/TheElderScrollsIVOblivion Oblivion]]'' and ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]'', while the transformation itself is still involuntary, it is possible to avert GlamourFailure and maintain TheMasquerade by feeding regularly, which allows you to maintain a mortal appearance.
** This is also true for becoming a [[OurWerewolvesAreDifferent werewolf]] in each game where it is possible, with the exception of ''Skyrim'' (as the particular type of lycanthropy there allows for [[SuperMode voluntary transformations]]). In ''Daggerfall'', you transform one a month and [[HorrorHunger must kill a sentient being]] during that night. In ''[[VideoGame/TheElderScrollsIIIMorrowind Morrowind]]'''s ''Bloodmoon'' expansion, you transform nightly with the same "kill a sentient being" rule. In either case, failure to kill someone while transformed causes you to awaken the next morning in a severely weakened state.
* In the ''Franchise/JakAndDaxter'' series (all games but the first), Jak is infected with a substance called Dark Eco and transforms into a hulking, monstrous version of himself when [[HulkingOut sufficiently angry]] or distressed. He eventually learns to control it to some degree. The same thing happens to [[spoiler:Daxter]] during ''The Lost Frontier''.
* ''VideoGame/BaldursGateII'' contains many examples of shapeshifting, mostly voluntary (class abilities) or offensive (Polymorph Other, aka Baleful Polymorph), but there are several involuntary ones as well. The best example is the Slayer transformation, which can be triggered voluntarily but also happens involuntarily after certain events or dreams. Another example is the description of the Shapeshifter class, which specifies that the Shapeshifter has voluntarily inflicted themselves with the sort of lycanthropy that causes involuntarily shapeshifting into a Werewolf, but then studied for many years to learn to control said transformations to make them voluntary, at the cost of failing to learn any other shapeshifted form.
* In ''VideoGame/DragonQuestVI'', [[spoiler:Amos]] turns into a monster every night due to a monster bite he received. The party can seek out Seeds of Reasoning, giving him the ability to control his monster transformation [[spoiler:and prompting him to join your party]].
* You can become one temporarily in ''VideoGame/NetHack'', by wearing a ring of polymorph, or permanently by ''eating'' it. Combining it with a ring of polymorph ''control'' does exactly what it sounds like, making you a VoluntaryShapeshifter instead.
* ''VideoGame/MoshiMonsters'' has the two species Little Red Riding Wolves (who are wolves that turn into little girls whenever the moon is full) and Wonky Wizards (wizards who have PowerIncontinence and sometimes turn into Pixel-Munching Snafflers, another type of Moshling).

[[folder: Web Comics]]
* In ''Webcomic/SluggyFreelance'' Aylee will occasionally have to wrap herself in a cocoon and emerge in a new form, though usually retaining a green skin tone and vaguely reptile/dragon like features. This was originally done because Aylee's first form was too close to the Xenomorphs from ''Franchise/{{Alien}}'' to be copyright-friendly, but has since been used as an important plot point or simply [[RuleOfFunny an excuse for a gag]].
* Kieri, an angel in ''Webcomic/SlightlyDamned'', was cursed by a guardian and turned into a snow bunny (subsequently nicknamed "Snowy"). The curse is weak enough for her to generally control it, but she does regularly transform ("poing!") into her bunny form at inopportune moments, such as any time she gets excited, [[http://www.sdamned.com/2010/08/08282010/ suddenly startled]], or starts [[http://sdamned.com/2007/09/09232007/ having a sneezing fit]]. Or if she just needs some [[CutenessProximity puppy dog eyes]].
* The changes in Jules from ''The Key to Her Heart'' are controlled by his/her emotional state, over which he's learned [[VoluntaryShapeshifting meticulous control]]; except, of course, [[RuleOfFunny when it's funny]].
%% Flute Cop from Webcomic/AxeCop is not an example -- he gets transformed into a variety of things as a RunningGag, but the reason for it is never explained.
* In ''Webcomic/ElGoonishShive'', there are multiple examples. Elliot, for example, has shapeshifting GenderBender powers, but he's at a stage where his body doesn't know its limits, so basically, he needs to transform every day to burn off excess magical energy, or else it'll overload at some inopportune moment, causing him to involuntarily transform with barely any warning.
* ''WebComic/EightBitTheater'': Red Mage has this happen to him late in the series. He randomly shifts between himself and a [[BuffySpeak flowery...tentacled...thing...]] that resembled a monster the team had previously encountered.
* ''Narbonic'' (and, later, ''WebComic/SkinHorse'') features Artie. Normally a (superintelligent) gerbil, [[MadScientist Helen]] decided to send him to break up a fight between [[ArchnemesisDad her mother]] and [[PsychoForHire her intern]], which necessarily involved giving him an ActionHero human form. After which he discovered that he transformed back into it whenever he hiccuped. Like Jules above, he eventually masters the art of transforming back and forth at will, [[RuleOfFunny except when it's funny.]]

[[folder: Web Original]]
* ''Roleplay/GlobalGuardiansPBEMUniverse'': Both Fenris and The Beast are villainous werewolves who have a hate on for the world that cursed them into being monsters. They are both villains ForTheEvulz rather than for money or power.
* For whatever reason, Sonic shapeshifts into several PlatformGame protagonists during ''VideoGame/SonicTheHedgehog2SpecialEdition'''s Metropolis Zone.

[[folder: Western Animation]]
* In ''WesternAnimation/AlienatorsEvolutionContinues'', as a result of him volunteering as a human guinea pig for finding a cure against the Genus, Wayne Grey undergoes random mutations (including growing extra limbs, splitting into more copies of himself, or becoming animal-like in appearance) every time there is a high concentration of alien cells in the surroundings. In one particular episode where the aliens grow out of control and briefly take over the whole world, he kicks into overdrive and explodes into a pink goo. In the final episode, the whole team gets sent on the Moon. Makes you wonder what the hell a ''two-headed spacesuit'' was doing in a space shuttle.
* Various ''Franchise/{{Transformers}}'' have had occasions where they lose control of their transformations between robot and alternate modes. Most commonly, this happens when they're hit hard enough, or as a reflex when one is startled. ''WesternAnimation/BeastWars'' is rather fond of the former.
* ''WesternAnimation/AmericanDragonJakeLong'': In one episode Jake begins to shift randomly from human to dragon, sometimes [[PartialShapeshifting one body part at a time]]. Application of "liquid plot" does this once, revealing his identity to his worst ''human'' enemy.
* Early in ''WesternAnimation/DannyPhantom'', Danny has trouble controlling his powers and sometimes goes partially ghost at random. Leads to his pants falling down at one point, memorable for a line that followed later that episode. The beginning of the episode "Identity Crisis" ''really'' emphasized this with Danny's shape shifting abilities. Very amusing.
* In the ''WesternAnimation/TeenTitans'' episode "Haunted", Beast Boy (who is normally a VoluntaryShapeshifter) has had occasional mishaps, such as a series of transformations that occur during a sneezing fit from the common cold. Or the episode where Raven learns how to use her powers to force him to change into another creature against his will.
* ''WesternAnimation/{{Beetlejuice}}'', from both cartoon series of the same name, changes constantly based on any wordplay to be found in his dialogue, apparently by force of habit. In one episode, some of the bad guys he faces exploit this by tricking him into saying "I'm coming apart at the seams", and then scattering his body parts when he literally falls apart.
* Similarly, ''WesternAnimation/{{Bonkers}}'' in one episode caught "literalitis", a disease which caused him to take the form of any idiom he heard. In another episode his first partner, Detective Lucky Piquel, caught "toon flu" and turned into this little three-inch high character when he sneezed.
* The main character of ''WesternAnimation/TurboTeen'' shapeshifts into a ''talking car'' when his body temperature rises, always at inopportune times.
* WesternAnimation/DarkwingDuck gets zapped with an experimental TransformationRay in one episode, and gains the power to turn into anyone he looks at. Downside is, [[PowerIncontinence he can't turn it off]]. And this is only one of many episodes of ''Darkwing Duck'' with this trope as the premise.
* In the episode "Dexter's Date," ''WesternAnimation/{{Freakazoid}}'' is zapped at a television station and cannot change back into Dexter Douglas, leaving his date waiting - and turning instead into random celebrities. (Fortunately, he turns into a blue Louis Armstrong just in time for his lines in the huge splashy ''"Hello Dolly"'' musical number parody. Don't ask.) The weird part is he always has his own voice, except for the Louis Armstrong bit.
* A TV series titled ''Monster by Mistake!'' features a main character who is a young boy named Warren, Warren turns into a blue monster whenever he sneezes.
* The episode of ''WesternAnimation/BatmanTheAnimatedSeries'' where Batman manages to ''guilt'' Clayface into doing this, by showing him clips of all the roles he's played in the past...and as Clayface remembers each one, he's turned into that character uncontrollably, until it literally turns into a type of torture: Clayface begging Batman to stop, but unable to until he's exhausted and supposedly capturable. It's debatable whether Batman was trying to get this reaction, since he'd already seen Clayface involuntarily start shifting into Batman upon their first meeting. His look of surprise suggests that he may not have expected such a ''strong'' reaction. Though, given the way the episode ends, it's equally possible that Hagen was simply playing to his audience: Batman. He ''was an actor'', after all....
* In ''WesternAnimation/ProjectGeeker'', Geeker is a genetic shape-shifter who [[PowerIncontinence can't control his abilities]]; he sometimes collapses into a puddle when he panics; in one episode, he sleep-walked through the city for several nights -- in {{Kaiju}} form.
* Dingo of ''WesternAnimation/SonicUnderground'' had the ability of transforming into virtually any other object or person, though these are invariably orange in color. His transformations are completely under control...of his partner Sleet, that is, not himself.
* WordOfGod has it that, in the ''Franchise/{{Transformers}}'' metaseries, Primus, Unicron, and the Original 13 Transformers's bodies automatically change to fit the physics of whatever universal stream they enter (similar in effect to a FisherKingdom, but caused by themselves, not the universe they enter). Primus and Unicron stop there, but the other 13 change further to fit the specific idiosyncrasies of the local Transformers. For example, when The Fallen is in the G1 universe, he looks blocky, and in the live action movie universe he looks more thin, lithe, and pointy. Also, in G1 he is [[IncendiaryExponent on fire]], while in the movie universe, due to physics, he is merely glowing red-hot.
* ''[[WesternAnimation/TeenageMutantNinjaTurtles1987 Teenage Mutant Ninja Turtles]]'': During the last two seasons of the first cartoon, this begins happening to the turtles themselves: at inopportune moments, they transform into monstrous, mindless forms. At the same time, the turtles make a new ally in Carter, who also suffers from his own kind of involuntary shapeshifting, albeit one in which he keeps control of his faculties.
* An episode of ''WesternAnimation/TheFairlyOddparents'' has Cosmo shapeshifting against his will due to his "Fegiggly Gland" working wrong.
* Chuck Jones' bizarre late-entry ''WesternAnimation/LooneyTunes'' "I was a Teenage Thumb" has a wizard with the hiccups who transforms into different random things with each 'hic' - a lamppost, a touring car, a hot-air balloon...
* WesternAnimation/{{Kaeloo}}'s Mr. Cat is one of these, his transformations into random objects usually brought upon by Kaeloo beating the stuffing out of him.
* On ''Film/AttackOfTheKillerTomatoes,'' Tara Boomdeay gets turned into a tomato when she touches salt. She turns back into a human girl after having pepper sprinkled on her and she sneezes.
* In the Al Brodax WesternAnimation/{{Popeye}} cartoon "The Wiffle Bird's Revenge," the Wiffle Bird casts a spell on Wimpy, making him turn into a werewolf when he says the word "hamburger."
* In ''WesternAnimation/AladdinTheSeries'', Genie comes down with a case of PowerIncontinence where his sneezes cause random magical effects to anything nearby, covering his nose when he sneezes instead caused him to transform randomly (and uncomfortably).
* Most ''{{WesternAnimation/Gargoyles}}'' turn to stone during the daytime; [[BigBad Demona]] turns into a human instead, thanks to a spell cast on her by [[JackassGenie Puck]]. She can't induce or repress this transformation; it happens every day when the sun rises, and reverses when the sun sets. Demona hates her human form (like she hates [[FantasticRacism everything human]]), but that doesn't mean she's not perfectly willing to take advantage of it when it comes in handy for getting what she wants.
* In ''WesternAnimation/TheAmazingWorldOfGumball'', [[spoiler:Penny Fitzgerald]] turns out to be a shapeshifter whose form [[spoiler:underneath her peanut shell]] is based on her self-image. She's rather self-conscious about it, which indirectly leads to her mimicking the way people describe her (or that she thinks they're describing her).
* ''WesternAnimation/StevenUniverse'' is {{half|HumanHybrid}}-Gem, an [[TheAgeless ageless]] race with VoluntaryShapeshifter powers that he [[HowDoIShotWeb has yet to master]], which has caused him problems on occasion:
** In "Cat Fingers", his first attempt at shapeshifting goes awry and he gradually turns into a [[BodyHorror writhing mass of cats]].
** "So Many Birthdays" demonstrates that he's literally as old as he feels; in other words, if he feels old, he ''is'' old. He ends up nearly aging himself to death via PowerIncontinence.
** "Steven's Birthday" takes it in the opposite direction; Steven's literally as ''young'' as he feels, which leads him to a troubling revelation: [[spoiler:physically, he hasn't actually aged in ''years''. He later attempts to shapeshift himself into the "correct" age, which backfires due to the strain it places on his body, reverting him to infancy]].