This can occur in the process of both involuntary and Voluntary Shape Shifting, and the final form, if there is one, doesn't have to be horrific. Even turning a person into a Ridiculously Cute Critter can involve Transformation Horror along the way. What matters is that the process of the transformation is unpleasant to witness, and horrifying just to imagine experiencing.
There are several standard forms of Transformation Horror:
- Mutation Horror: slowly accumulating chaotic mutations. The victim gradually becomes increasingly twisted and deformed due to the growing influence of The Corruption, exposure to nuclear waste, Mutagenic Goo, or The Virus. There is no "end form", only ever-increasing levels of Body Horror usually involving asymmetric and chaotic changes and tumorous growths. This variety tends to end in either death, FaceMonster Turn, or the victim's best attempts at screaming.
- Horrifying Metamorphosis: Slow Transformation into a known end form. Often part of the Viral Transformation process or a particularly unpleasant form of Metamorphosis or Baleful Polymorph. The victim experiences a disturbing slow change into his new form. The end result does not have to be body horror, but the process of adopting an entirely new body plan is likely to involve quite a bit of body horror.
- Traumatic Transformation: Rapid Transformation into a known end form. Some transformations condense all the horror of a targeted slow transformation into a brief, squicktastic Transformation Sequence. Often emphasizes the face and visibly reshaping skeletal structures, and is usually accompanied by the sounds of popping bones and rearranging organs. Nearly always painful or disorienting. Common in Darker and Edgier Animorphism: The transformation of a werewolf, for instance. note
- Terminal Mutation: Targetless and Fast. A particularly nasty Cruel and Unusual Death involving rapid degeneration or mutation until death. See Rapid Aging, I'm Melting!, and Shapeshifter Swan Song for just a few of the possible causes. Examples of this form should be placed on their respective pages unless they are particularly noteworthy as transformation horror as well.
- Mix And Match Mutation: Sprouting Combat Tentacles or a Shapeshifter Weapon can be disturbing enough, but when more and more are added to the mix you have the recipe for a Shapeshifter Mashup. Even more horrifying if it's involuntary, such as in the case of Power Degeneration, or an Adaptive Ability going totally haywire.
There are several layers of reasons why people find this trope disturbing:
The most obvious is that transformation can be very Squicky: even in the case of one human becoming another human, facial features and major bone structures have to distort and rearrange. This naturally means that the course of a transformation tends to at least pass through the Uncanny Valley at some point, and quite often takes the scenic route.
Transformation also invokes the fear of losing control of your own body, or having it turn against you: Transformation Horror is unusual among the fantastical forms of horror in being just as much an Adult Fear as a childhood fear, because it has so many parallels and examples in Real Life. Puberty, unexpected changes in people around us, the ravages of old age, slowly losing one's own identity to mental illness, or worse, having a loved one turn against you, are all too real events experienced by most people at some point. All it takes to make horror from them is exaggeration. Even more extreme forms such as Mutation Horror or Terminal Mutation invoke our fears of disease and decay; in a sense, this trope is why we find diseases like cancer, rabies, leprosy, and the bubonic plague exceptionally terrifying: they transform a victim physically and mentally from the inside out.
Not all transformations are necessarily horrific; this trope can be averted in any number of ways. Lighter and Softer universes tend to have relatively tame transformations leaving any disturbing elements to the imagination. On the other hand, in Darker and Edgier universes, even Voluntary Transformations tend be traumatic for everyone involved, and depicted in all their disturbing glory. The medium can have a huge bearing as well: distortions that would be Nausea and/or Nightmare Fuel in live action can be fairly innocuous in a cartoon.
The causes and circumstances of the transformation can make a difference as well. A character slowly turning to stone can be fairly mild visually, but played for Psychological Horror; an otherwise disturbing transformation can be mitigated when it's the result of a character Cursed with Awesome activating their Lovecraftian Superpower or receiving a Power-Upgrading Deformation.
An example of how this trope can be intentionally both invoked and averted is the Transformation Comic genre, with various comics averting this trope for fanservice or comedy, playing the trope straight as Fan Disservice to maintain a serious tone, or even alternating between the two.
Compare Clone by Conversion, Transflormation, Viral Transformation, Painful Transformation, Slow Transformation, Transformation Sequence, Transformation of the Possessed, and Transformation at the Speed of Plot which often overlap.
Compare and contrast Baleful Polymorph, which sometimes overlaps with Transformation Horror. The distinction is that the victim of a Baleful Polymorph has become something else against their will, while Transformation Horror is about becoming something else in a disturbing way.
Contrast Nothing Is Scarier and Fridge Horror for transformations that aren't actually shown/described, and Teleporter Accident for similar things happening instantaneously. Bit-by-Bit Transformation can be used both to subvert this trope by spacing out the squick into tolerable doses, and to exaggerate it by combining Horrifying Metamorphosis and Mix And Match Mutation.
- In Naruto, this happens when Naruto goes into four-tails mode, especially when his skin peels off.
- This happens to Tetsuo in AKIRA after being wounded by Kaneda during their fight at the stadium, as Kaneda tries to finish him off he starts twitching and moaning in pain when suddenly his mechanical arm bursts open and sprouts tentacles, he becomes gigantic and bursts out of his clothes, and he mutates into a massive blob creature that consumes everything in his path including his girlfriend Kaori and he is unable to control himself.
- In Princess Tutu, Rue's Transformation Sequence into Princess Kraehe involves lots of thorns and pain...
- The scene near the end of Devil Man The Birth where the party goers in the night club get possessed by demon spirits after Ryo spills their blood, the worst happens to two girls, the first has her jaw dislocate and grow fangs, her eyeball pops out of it's socket and wiggles like a worm, and her breasts to grow eyeballs and fangs, and the second one transforms into a hideous demon covered with spikes with her severed head perched on top of her new one, and her eyes still blink which freaks out Akira.
- In Made In Abyss, ascending from the titular cavern causes progressively more extreme ill effects as a person reaches lower levels. By the Sixth Layer, the Curse of the Abyss causes its victim to undergo a horrific, violent transformation into something not even close to human. Often, this outright kills the person, falling under Terminal Mutation. The viewer is shown what this looks like in a later episode of the anime (with a character who technically survives), and it's not pretty.
- Druuna: The "Morbus Gravis" is a viral disease that turns people into horrible mutants and has no known cure. Even worse, some people who are affected by it are still completely lucid after the transformation, human souls trapped in a monster's body.
- The Call of C'Russo: Donald and his nephews are partially mutated into octopoids when Ar-Finn wakes up from his slumber.
- Whenever the ponification process is described in The Conversion Bureau: The Other Side of the Spectrum, it's going to be this. However, it's not a free action - Mercy Kills are a common sight in the fic and its side stories, and Amputation Stops Spread. Special mention goes to the trials for the Flawed Prototype versions of the potion, which were so shocking and horrifying beyond words that it's almost impossible to fully describe.
- Although it isn't shown on screen, Lyra being turned into a human by a miscast spell in Helping...Hands? clearly qualified as a Traumatic Transformation, especially given Trixie's description of Lyra's new form. And her transformation back into a pony is described, in gruesome detail.
- A Minor Miscalculation has Ryuko's transformation into her empowered berserk form. The process is quick, but grotesque: her bones and spine snap, her skin starts melting into Senketsu and her weapons, and blood (both human and decidedly different types) starts boiling out of her skin.
- Jade Chan in Webwork takes eight long, painful and humiliating years to transform into a spider demon. Parts of the change being so painful that she has to be placed in a coma to avoid the pain of her skin and bones melting while she grows an exo-skeleton. The initial act that started the change is so graphic that the author marked the section where is starts and ends so readers can skip over it.
- From The Bridge, Monster X's involuntary transformation into Kaizer Ghidorah is this. He goes from a bipedal, 58,000 ton Draconic Humanoid to a quadrupedal, 100,000 ton winged, three headed dragon. Growing all that muscle mass, scales, and skeletal changes is nothing short of agonizing; being described as his body tearing itself apart and putting itself back together repeatedly. For instance, his wing bones need to tear their way out of his back.
- In the Thriller Bark arc of This Bites!, Gecko Moria tries to turn himself into a dragon with "Nidhogg", feeding his shadow other shadows and then reshaping it, thus himself, with Shadow Revolution. The emphasis is on "tried". The sounds Moria's body makes when undergoing the transformation are nauseating. When Cross gets a peek at Moria, he nearly vomits on the spot noting that the end result can't be called Moria or a dragon. Chopper, the Straw Hat doctor, is horrified at the amount of physical trauma the Warlord put himself through.
- Snow White and the Seven Dwarfs, the first movie in the Disney Animated Canon, has the evil queen using a Human Shifting potion to turn herself into an old hag as a disguise.
- A few years after Snow White, Disney's next movie Pinocchio upped the ante with Lampwick's transformation into a donkey. He doesn't know what's happening at first (and even Pinocchio thinks it's the booze), but once he does, he begs Pinocchio for help, calling out helplessly for his mama before he devolves into a wild, braying, panicked mess.
- Played for Laughs on A Goofy Movie, where Max dreams that he's turning into... his father.
- In Penguins of Madagascar, the Medusa Serum turns penguins into hideous creatures with mismatched body parts, extra eyes, and other deformities.
- Frankenweenie has plenty of examples, especially Mr. Whisker's transformation into a vampire-cat hybrid, thanks to accidental fusion of cat and bat atoms through teleportation. Bonus points for referencing An American Werewolf in London and The Fly (1958).
- An American Werewolf in London almost single-handedly popularised this tropes' connection to werewolves.
- In District 9, Wikus slowly transforms into a prawn.
- In The Brothers Grimm, a girl named Sasha gets her face taken away by some mud cursed by one of the Mirror Queen's crows, then the mud turns into a monster pursuing the now faceless Sasha; at the end of the scene the mud absorbs her turning her into the Gingerbread Man, then tastes a bit of its body thinking it/she tastes good.
- The Howling. Another particularly graphic example werewolf transformation, with the squick factor turned Up to Eleven thanks to effects artist Rob Bottin. His next gig would be The Thing (1982), widely considered a crowning achievement in body horror effects.
- In The Matrix, any human possessed by an Agent transforms into that Agent's appearance in a Silly Puttystyle rearrangement of anatomy. Taken Up to Eleven by Agent Smith's Clone by Conversion ability in the later films, as the process takes place much more slowly and the victim appears to be fully aware of the fact that they are being overwritten by the Agent as it happens.
- The trailer for Dracula Untold, shows us a close-up glimpse of Vlad's face peeling and shedding away during his transformation into a Vampire. This is a case of Trailers Always Lie as this happens when he is exposed to sunlight later in the film.
- Willow: Of the Horrifying Metamorphosis variety, when Queen Bavmorda magically transforms an entire army into pigs. It's made explicit that the transformation doesn't affect what the victims are wearing, making a slow, painful process worse with constriction by clothing and medieval armor as they change shape.
- The Fly (1986) milks this trope for all it's worth, as Seth Brundle slowly, horrifically mutates into a monstrous humanoid fly over two hours. Beginning with having teeth fall out, in the later stages, the transformation terminates with extra limbs bursting through his torso, the flesh on his hands peeling off, as his facial features melt and slough off to reveal an insectoid face. The fly monster ultimately is transformed a second time, being teleported with broken machine parts and ending his life as a mechanical hybrid creature.
- The Indiana Jones movies did this at least twice to characters seeking Public Domain Artifacts that turned out to be too powerful for mortal hands. At the end of Raiders of the Lost Ark, when Those Wacky Nazis open the Ark of the Covenant, its divine power strikes them dead: one man's face shrivels up, one man's face melts, and one man messily explodes. Indiana Jones and the Last Crusade did something similar in the shrine of the Holy Grail, which turns out to be hidden among dozens of other goblets; the guy who picks the wrong one dies by Rapid Aging. Remember, kids: Holy Is Not Safe.
- The 1990 film "Metamorphosis: The Alien Factor" is a particularly long and gruesome film centered entirely around a scientist accidentally mixing their cells with a mutated alien after being bit by the monster. The next 40 minutes are said scientist's horrifically slow, irreversible, bloody, and painful mutation into what could only be described as a hybrid between Biollante from Godzilla and G Birkin's final form from Resident Evil 2. Even being shifted back human at the end of the film from an electron accelerator only causes the mutation to go haywire and mutate into an even worse monster. Needless to say, neither form could be described as bipedal or humanoid in the slightest.
- XX: In "Don't Fall", the transformation Gretchen undergoes into human/spider hybrid is extremely rapid and painful.
- Invoked and inverted in Animal Farm: The other animals are horrified to watch the pigs, who were satirical allegories of Communist dictators, gradually become indistinguishable from the humans they overthrew, though the pigs barely seem to notice.
- Animorphs. Many, many examples throughout the series, played straight to the point of a Black Humor Running Gag. Most of the Animorphs freak out the first couple of times they try particularly exotic morphs, but after a while they get used to it. Shining examples include:
- Fish: You lose all your limbs and frequently spend a few moments either underwater with lungs or out of it with gills, and on at least one occasion a character spent several seconds with neither.
- The undiluted Transformation Horror of insect morphs. One has to become a Giant Insect/Human hybrid for the duration of changing from a human to an insect. (See The Fly if it hasn't hit you why that's horrifying yet.) Also, note that insects don't have eyelids, and frequently do have panoramic vision, so you have to watch it happen.
- The defiance of this trope is Cassie's, and one Andalite character's, talent. Rather than looking like several crimes against nature she can make the transformation nice to look at, even beautiful.
- In Black Bullet, this happens whenever some poor sap transforms into a Gastrea. His body bulges unnaturally as he transforms.
- The Half Human Hybrids in H.P. Lovecraft's The Shadow Over Innsmouth become more and more like their Fish People ancestors as they age.
- Invoked in the Discworld novels: Angua absolutely forbids anyone to watch her while she is transforming from human to werewolf and vice-versa. Especially her lover Carrot, on the grounds that what he may see could put him off her for life. One man who did watch ran away, and went to sea to put the terrible sight behind him.
- Thinner by Stephen King: An obese lawyer begins losing weight after hitting a gypsy's daughter with his car. The friends who help him cover it up develop their own body issues.
- In The Southern Reach Trilogy, expedition members entering the Eldritch Location Area X are warned to avoid "contamination" in vague, unspecified terms. They only learn the exact nature of the contamination when their bodies begin transforming. Most turn into animals similar to the existing local wildlife, but sometimes the process goes wrong and results in a hideous abomination.
- The Change that werewolves go through in Red Moon Rising. It involves multiple bones breaking, permanent disfigurement that lasts even into human form, and is incredibly painful. The fact that it takes place in strict and militant government compounds certainly doesn't help.
- Eden Green graphically depicts most varieties of transformation horror; the central theme of the book is Horrifying Metamorphosis. In addition, the rationalist main character imagines many possible scenarios in which the needle symbiote can ruin a person forever.
- The Girl from the Miracles District has a Traumatic variety with Nikita's transformation into a berserk, and the story delights in providing the reader with an in-depth, vivid description of what exactly is hapenning to Nikita's body and mind.
- United States Of Japan introduces a lovely virus that rewrites the victim's DNA. Not into anything in particular: imagine spamming 1s and 0s across a hard drive to understand the effect, which is painful, gruesome to watch and inevitably fatal. It's used to interrogate traitors.
- In Loyal Enemies, Shelena describes her transformation from human to wolf and back as non-painful but horrifying to look at, as her bones have to change their structure and function and all of this happens in the open. She likens it to watching someone being turned inside out. Rest doesn't manage to look away quickly enough the first time she transforms in his presence and has to make a dash for the nearest bushes to vomit up his breakfast.
- Kent J. Starrett tends to do this, but it's most prevalent in his adult works; particularly the Sci-Fi Horror anthology Human Resources.
- In The Gordian Event by Lee Deadkeys, people infected by the Gordian parasite mutilate themselves at the onset of infection, bloat to the point of splitting their skin and have their internal organs and bones partially digested as the parasite grows. Rudy does an in-depth analysis of the end result, pointing out the internal damage and amniotic fluid that sustains the host through the otherwise fatal transformation.
Rudy: See here, how the ribs are spread and bulged? Look closer at the rib bones, do you see this pocking? I believe that is marrow showing through thin spots on the bone.
- Harry Potter:
- The Polyjuice Potion temporarily transforms the user's body to look like someone else. We first see it in Harry Potter and the Chamber of Secrets, with lovely descriptions of Harry's insides "writhing as though he'd just swallowed live snakes," followed by his skin melting and bubbling as it transforms. Later, in Harry Potter and the Goblet of Fire, the man we thought was Mad-Eye Moody reverts to his true form when the potion wears off. We get a description of Moody's wooden leg and magical glass eye popping out of the transforming body as the impostor's real leg and eye grow back in.
- Harry Potter and the Prisoner of Azkaban has Professor Lupin's transformation into a werewolf. Also, the stories of his transformations as a child coupled with the bloodstains and destruction in the Shrieking Shack are pretty disturbing, especially since he has to go through a similar process every single month.
- Damned thieves in The Divine Comedy are turned into snakes and have to regain human form by attacking others and eating their essences. The poet gives a vivid description of how each part of the human body devolves into the form of a serpent while the serpent painfully splits apart into a man.
- The Outer Limits (1995):
- "Quality of Mercy": During a future space war, a female cadet is locked up with a Major from another division when they're both captured by the aliens. The aliens start to transform her into one of them so they recruit her and use whatever useful knowledge she possesses, and her body gradually mutates further. Until the ending reveals that they're changing her back, and she was sent to spy on the Major so that he'd reveal the location of their forces.
- "The New Breed": A man injects himself with experimental nanotechnology to cure his pelvic cancer. The problem is that they don't stop there, or even at healing old scars and adjusting his eyesight so that he doesn't need glasses anymore. For instance, they interpret his inability to breathe underwater as a physical weakness, and he develops gills. It only gets worse from there.
- Raven and Chelsea slowly turn into cows in the Halloween episode of That's So Raven. They don't exactly take having long pointy ears and white, furry tails very well...
- Hilariously Subverted in an episode of Wizards of Waverly Place when Justin is transformed into a werewolf by his new girlfriend. He freaks out over this trope applying, but she tells him the change is actually quick and painless. Sure enough, by the time the camera pans back to him, he's already changed without even noticing.
- In the first episode of the second series of Misfits, the shapeshifter's transformation sequences involve her clawing at her face and screaming in agony as the lights of the locker room flicker behind her. Made more unsettling by the fact that her eyes turn completely black in both pre- and post-transformation forms.
- Hemlock Grove has some of the goriest werewolf transformation sequences in all fiction. The person doesn't just grow a lot of hair, canine teeth, and stretched limbs, it's more akin to a butterfly transformation with their entire human body getting ripped off so the wolf underneath can burst out.
- Doctor Who: In "The Ark in Space", Noah finds himself slowly undergoing a horrifying transformation in a Wirrn after being infected by one.
- The New Orleans swamp-dwelling Roux-Ga-Roux werewolf changes between its forms by ripping its own skin off, revealing the skin underneath.
- Celtic Mythology's Cú Chullain had an ability called "Warp Spasm", which basically made him The Incredible Hulk, but with a Nightmare Face. Standard "go from a regular guy to a beefy mass of Unstoppable Rage," with a side order of Eye Scream-one eye would swell until it popped out on the nerve, the other would shrink and recede into his skull. His mouth split (whether like mandibles or Glasgow Grin I don't know), his temples swelled up, his knees reversed orientation, and his hair got spiky.
- In Warhammer Fantasy and Warhammer 40,000, notable servants of Chaos tend to accumulate mutations as rewards (or punishments) from the Chaos Gods, and/or through exposure to raw Chaotic energy. Some of these mutations have a clear end goal, like the champion taking on the appearance of one of their god's daemons, but others follow no set pattern. Those who have received too many "gifts", or have fallen out of favour with the gods, risk devolving into insane, shapeless horrors called Chaos Spawn.
- Most of the early-mid game opponents in Bloodborne are some kind of werewolf-like creatures, who clearly were once men. When encountering Vicar Amelia, you actually get to see how exactly the transformation goes; and even a Gory Discretion Shot can't hide the fact that it isn't pretty.
- Traumatic Transformation happens when you put on the Deku, Goron, Zora, or Fierce Deity masks in The Legend of Zelda: Majora's Mask. Thank goodness it's possible to skip them after you see it for the first time.
- Similarly, the first time Link transforms into a wolf in The Legend of Zelda: Twilight Princess appears very painful and disorienting for Link. Like Majora's Mask, however, transforming after this first cutscene is instantaneous and, presumably, painless.
- This trope is the main problem faced by the characters of Pandora's Tower. The protagonist's girlfriend, Elena, has been cursed to turn into an Eldritch Abomination, and the main goal of the game is to stop it before it's too late. The horror part is in full effect here, with the transformation growing more gruesome every second you waste.
- The Dead Space franchise is largely built around this trope: all of the Nightmare Fuel that's trying to kill you is the result of a mutagenic plague commandeering recently dead bodies for arts and crafts projects. The kicker is that we learn in Dead Space 2 and 3 that you just have to be mostly dead.
- Erazor Djinn while he transforms into Alf Layla wa-Layla in Sonic and the Secret Rings.
- Final Fantasy VII's resident Mad Scientist Dr. Hojo, and what happens to him when he downs one of his serums when Cloud and Co face him. Back in the day when FF7's graphics was top of the line, this looked horrifying.
- Many Sorceresses in Final Fantasy VIII appear to slowly mutate into no particular end form. One unnamed Sorceress boss looks less like a human being and more like a giant grub. Ultimecia's (quickly changing) One-Winged Angel forms deserve a honorable mention: first she fuses herself with a giant lion-like beast, and later turns into a form no less repulsive than the aforementioned grub woman.
- During Parasite Eve series Square again provide graphic depictions of this trope in their high-quality CGI movies, starting from rats, and ending with humans. That German Shepherd from first game deserves special mention. Poor thing.
- In Diablo II, the Dark Wanderer's body has already been altering slightly due to his nasty Demonic Possession, but in the cinematic for Act IV, he goes through a transformation that Marius, who followed the Wanderer all this way, describes as "not meant for mortal eyes." At first, the skin on his face starts flowing, and then most of it is hidden as he transforms into Diablo in his full formnote .
- Body Harvest: In the Siberia level some poor sap is being mutated into a Giant Spider-man hybrid by the aliens. Adam can even talk to him as he's lying helpless on a table.
- The Formless Flesh in Darkest Dungeon is a horrible, constantly shifting mass of demonically possessed pig flesh, which shifts every turn - sprouting heads, hearts, spines and tentacular backsides at random. It's actually even uglier than it sounds. And while we don't get to see much of the transition, the Countess from the Crimson Court DLC actually weaponizes it when transforming into her true form, as this is a game where Stress is a mechanic and witnessing her go from mostly human to horrendous insectoid abomination is not a pretty sight at all for the four heroes.
- Runewriters: Severian and other shapechangers can turn themselves into various animals. This includes aberrants, the resident lovecraftian horrors. Watching someone turn into one on-panel is less than comfortable.
- Nebula: Used in different ways for Sun and the dwarf planets consumed by Black Hole.
- Sun is very slowly changing into something else, growing physically much larger and (as he is made of fire) burning hotter, and he is conscious and worried by the fact that his personality is changing along with his body and turning him into something very hungry and constantly on the edge of fury.
- The transformation for dwarf planets is very rapid and makes them look outright monstrous (among other things, growing distorted extra limbs can happen), with their minds either subsumed or controlled by Black Hole once the transformation is done.
- This is a favorite trope of the SCP Foundation's community, and the collection contains many examples of all forms of transformation horror. Noteworthy examples include a sentient microorganism, The Clockwork Virus, The Seven Furs, and Gaia's Blood.
- Whateley Universe: Several of the students have experienced this to some degree or another due to their mutations, but four in particular stand out:
- Fubar, formerly 'Brainteaser', who had an encounter with... something... on the astral plane, which caused him to transform into a literally Lovecraftian creature which is unable to breathe air anymore. He's lived in a pool in the basement of Hawthorne Cottage for three decades now.
- Puppet, whose blood turned into a toxic green muck which is slowly killing her, thanks to a necromantic sacrificial ritual intended to turn her into the mage's super-powered catspaw. She has been on life support for over a year, as most of her major organs have shut down entirely, including her heart.
- Migraine, who attempted to use an experimental Devise to transform herself into an Exemplar, but instead was transformed into a Gigeresque insectoid monstrosity that was trapped in an immobile exoskeleton.
- Theophany, who, under the direction of a voice claiming to be God, transformed Folder into a girl with intention of making her his 'divine bride'. Folder's reaction when he attempted to consummate the marriage by force left Theophany looking like a crumpled piece of paper - alive, but horribly mutilated and distorted to the point that even Jobe was shocked.
- A .Gif file exists of a man doing the standard "Transform and Roll Out!" line from Transformers, and turning into an Organitek car- his spine and ribs pop out of his back to make him quadrupedal, his face tears into quarters to become the grille and headlights, his arms and legs become the fuselage, and it's best not to speculate on where the tyres come from.
- One episode of Danny Phantom has the main character trying to duplicate himself, only to horribly, horribly mutate himself: little heads on individual fingers, mouths for eyes, eyeballs sticking out and so forth. On the other hand, it is Played for Laughs.
- Men in Black: Alpha collects useful anatomy and additional limbs from alien species as he descends farther and farther into evil and madness. By his last appearance, he's pretty grotesque, and an excellent example of Mix and Match mutation.
- When Samurai Jack gets infected with a fleck of Aku, black spots start growing and spreading on his body, making his hands and feet clawed and gradually replacing his facial features with the Big Bad's while also making him do far more evil things. It takes him a long time to catch on, even after he starts arguing with himself, but he's plainly horrified when he sees it. At some point, Aku takes over his body so that only an eye and a small patch of skin around it is left, and Jack weeps.
- Episode C: After finding out he's her father, Aku forcibly (and painfully) transforms Ashi into a demonic version of herself, while Jack can only look on in helpless horror.
- Spider-Man: The Animated Series. Poor Spider-Man underwent quite the horrifying metamorphosis into ManSpider several times in the "Neogenic Nightmare" arc, with each iteration being more severe than the last, eventually developed into full-blown Mutation Horror. Later on, the Vulture absorbed Spidey's youth and powers... and also his unstable mutating DNA, meaning he sporadically changed fully or partly into the same creature.
- The Spectacular Spider-Man has Connors' transformation into The Lizard, especially the part where instead of compressing slowly, his head partially implodes to form his new lizard head.
- Happened to SpongeBob in "I Was a Teenage Gary" when that snail plasma turned him into a snail, and Squidward later followed suit.
- In Street Sharks, this pretty much is what gene slamming is all about. Every time a person is turned into a fish/human hybrid, it involves them twisting around, screaming in pain. And since most of the designs involve the heads being directly fused to the bodies with no necks, it means that the transformation involves the subject's head changing shape.
- The Avengers: Earth's Mightiest Heroes! episode "Gamma World" has The Leader turn various people into gamma-irradiated monsters. A few gruesome sights include the victims writhing in pain, The Wasp and Black Panther developing the features of their animal namesakes, and Iron Man's heart contorting.
- Garfield: His 9 Lives has the "Lab Cat" of segment 7 becoming a dog. In the original book it was scary but quick◊ but in animation, it's a Painful Transformation that even resorts to only his shadow in the final takes.
- Steven Universe had Steven trying to learn how to use his shapeshifting powers, and his first successful attempt was to turn one of his fingers into a tiny cat head. Then another of his fingers into a second tiny cat head. Things escalated a bit out of control from there.
- Played for Laughs in The Amazing World of Gumball episode "The Nuisance"; after a spree of good deeds, the Wattersons quite graphically turn into 60's-style white humans, except for Darwin, who turns into a dog. This even includes a part where their bare feet turn into shoes.
- Insects change form or size by shedding their skin and growing when their flesh is still supple. Sometimes this process fails. The results range from a bit odd to grotesque to downright Lovecraftian. And the insect's still alive...