Animorphism

"Ford, you're turning into a penguin. Stop it."

—Arthur Dent, The Hitchhiker's Guide to the Galaxy

A character is transformed into an animal, either completely or partially (like a Biological Mashup). The defining quality for this trope is whether their transformation was Voluntary Shapeshifting or not:

There are many characters whose ability to transform into animals is a special power. Several of these are Shapeshifters whose power is limited to animal forms, and oftentimes a set number at that. There are also quite a lot of Shapeshifting characters who can turn into anything, but prefer to transform into animals, presumably because you can get more done in the shape of a living being than something inanimate. Our Werebeasts Are Different covers werebeasts.

Others are characters unwillingly transformed into animals, usually as a punishment (ironic or otherwise) or Curse, more often than not by the dark magic of the Big Bad. In any case, regardless of species, the target is none too happy about being an animal. (Indeed, for some reason, characters are often just as upset over being turned into swans as they would be if they were turned into worms. There is an intriguing amount of Cursed with Awesome associated with this trope.) The target may lose the ability to speak, and must work hard to get the message to their friends about what happened. This is sometimes combined with a Freaky Friday Flip, leaving the animal's mind trapped in the human character's body (where Hilarity Ensues). This is frequently accompanied with some sort of time limit, after which it will be difficult or impossible to reverse the process.

In any case, a physical transformation into an animal may be accompanied by a mental transformation into that animal, more so if it was involuntary. It may also allow the character to use whatever skills and abilities (like a keen nose or ability to fly) are associated with that animal ... as well as whatever strange instincts or unhygenic behaviors may also be associated with that animal.

The transformation itself may be scientific in origin, or mystical. Popular mystical transformations include Werewolves and other Werebeasts, wolves (who may be confused for werewolves), or such chestnuts as a witch turning people into toads. And who can forget such classic fairy tales such as swan maidens or The Frog Prince? In fact, Animorphism is Older Than Feudalism, with The Odyssey describing Circe turning Odysseus' sailors into pigs.

See also Baleful Polymorph, from witch this is the consequence. Contrast with Humanity Ensues, the rarer inverse of animals transforming into humans.

Not to be confused with the Sliding Scale of Anthropomorphism. See also Petting Zoo People.

Not to be confused with anamorphism, either kind.

Examples of Animorphism include:

Voluntary Animorphism

Anime and Manga

All familiars, and Yuuno, in Magical Girl Lyrical Nanoha.
Ichigo of Tokyo Mew Mew is a borderline case. The intended effect of her cat genes is the ability to voluntary transform into a Catgirl; however, as her cat DNA starts to overtake her human DNA, she starts involuntary growing cat ears and tail when excited, and eventually begins to fully transform into a cat. Another recurring character in the show can become a cat voluntary, but only for a limited time.
Yoruichi in Bleach spends a lot of the series as a cat because she likes to. Most of her transformations to and from human are to mess with other members of the cast (like Ichigo).
One Piece has the Zoan variety of Devil fruits, which allow the eaters to transform into a certain animal depending on what the fruit is, as well as a half-human hybrid of said animal (and yes, even humans are counted as an "animal"). Most fruits have a certain "model" for animals that are in the same family (EX: Dog Dog fruit, Model Wolf), or different sub-branches like "Awakened" which is more beast then man, "Mythical" like a Phoenix, and "Ancient" like a T-Rex.
- Even inanimate objects can "eat" a Zoan Devil Fruit, they gain characteristics of living being and their corresponding animal's intelligence; they also can transform into the animal itself, and hybrid (in the absence of a better word) or their "original" object form.
Early in the series, Kotaro of Mahou Sensei Negima with his powers sealed revealed the ability to become a small puppy. Recent events show that he can, at full power, become a Super-Powered Big Badass Wolf.
Ai to Yuuki no Pig Girl Tonde Buurin is about a warrior style Magical Girl (think Sailor Moon, Tokyo Mew Mew, or Pretty Cure) whose magical form is... a super powered pig. She does this willingly, but grudgingly, in order to earn pearls for good deeds so that once she gets 108 of them she can become a human superheroine instead.
Essentially the entire point of +Anima.
In Ruin Explorers, Ihrie was cursed as a child so that she turns into a mouse whenever she casts magic. Fortunately, she carries along a medicine that can reverse the effects, though having a limited supply at any one time means she still has to choose her battles.
Pokémon has an episode in the Johto League saga wherein Ash meets a witch named Lily. She has a recipe for a potion that will let you read a Pokemon's mind, but needs some ingredients first. At the end of the ep, Ash is turned into a Pikachu, which is affectionately nicknamed Ashachu. It launched a hundred Fanfic sequels when that happened.
Rumiya and Ryo-Ohki in Pretty Sammy.
Some fairies in Fairy Navigator Runa have animal forms as well as human ones.

Comic Books

Snowbird from Alpha Flight is an Inuit demi-goddess who can shift into any animal, but it's always an albino female. For a time, she could only shift into creatures native to Canada (for that matter, she couldn't leave the country's borders without dying). Those restrictions faded with her immortality when she lost her virginity, but the writers seem to have forgotten this.
Viktor Romanov in Nikolai Dante can turn into a giant eagle due to his weapon crest.

Fan Works

In The Secret Life of the Backyard Kids, Tiffany transforms into a giant cat, and since Jorge is a Squishy Wizard, he calls his nanny and she tells him to transform into a panther. He not only does just that but does a Shout-Out to Michael Jackson.

Literature

Daine in Tamora Pierce's Immortals quartet is a shapeshifter thanks to her Wild Magic. She has increasing control over her transformations as the books go on, though she retains her human mind even within the animal shape.
- The problem of her keeping her human and animal self separate is briefly addressed in Wild Magic, but takes little time to fix once she tells Numair, the most powerful mage in the world, that she's having trouble.
One third of the premise of the series Animorphs. (The other 2/3 are Alien Invasion and Ragtag Bunch of Misfits.) Also the Trope Namer
Several characters in the Harry Potter series (such as Professor McGonagall and Sirius Black) are "animagi", who can transform into specific animals (McGonagall becomes a cat, Black a large dog). Unlike most instances, this practice is very strictly watched by the government (who keeps tallies on the number), and is said to be incredibly hard to do.
Wizards in Ursula K. Le Guin's Earthsea Trilogy books are capable of transforming into animals, though the process is dangerous. In one particularly memorable example, the protagonist Ged turns into a hawk in order to escape an enemy - and, forced to spend weeks in his new form, almost ends up getting stuck that way.
- absolutely hilarious when you think about the fact that Ged is played by Shawn Ashmore in the Syfy version of the first book, that Ashmore was Jake Berenson in the TV version of Animorphs, that Jake saves Tobias from a swirly before the first book... and that Tobias ends up stuck as a hawk (red-tailed hawk, to be exact) at the end of the first book.
Wizards in Nightrunner can turn themselves and others into an animal form that is said to be their "true nature." The fact that it can be done to others, of course, means it's not always voluntary.
Many of the evil characters in The The Caretaker Trilogy Trilogy are Half Human Hybrids of some sort, but the only one shown to actually be capable of turning into the animal whose traits he borrows is Colonel Aranha. For those who didn't get the Meaningful Portuguese Name, he turns into a gigantic tarantula.
In The Thief of Always, victims of the Big Bad turn into creepy, giant fish when their souls are removed. It's a gradual process.
The Were Hunters in Sherrilyn Kenyon's Dark Hunter series were created by a king using his children, animals, and Magic Genetics to create Shapeshifting progeny.
In the Xanth series, Dolph can turn into any living thing as his magical talent, while his grandfather Trent can turn any living thing into another living thing as his.
Dinah and Dorinda, the main characters of Eric Linklater's children's novels The Wind on the Moon, use a magic potion given to Dinah by a witch in order to transform themselves into kangaroos. They are, however, stuck in kangaroo form until they can locate the bottle with the potion to transform them back to humans, which leads to them being caught and put in a zoo. In the zoo, they also meet Mr. Parker, formerly a human detective, who was transformed into a giraffe for no apparent reason (he blames it on wishing he was taller back when he was human).
In the Chronicles of the Cheysuli series, the eponymous Cheysuli can turn into the shape of their Lir (a Bond Creature that is some kind of animal bear, wolf, hawk...) some can turn into the form of any Lir they want.
In Rick Riordan's The Heroes of Olympus series Frank Zhang a demigod son of Mars can be anything. According to Mars this means anything within reason, any living animal. This gift did not come from Mars however, but Poseidon, who is a distant ancestor on Frank's mother's side. His whole family can do it, and have for generations going back to Periclymenus a legendary Greek hero who Poseidon first bestows this gift on. Percy, Poseidon's actual son, is noticeably jealous of Frank's gift.
Everyone in The Last Dove can (somewhat) voluntarily shapeshift.

Live-Action TV

Manimal had a main character with transformation into animals as a special ability.
In True Blood there is a shapeshifter community. They can turn into any animal they want; they just have to see it in order to "copy" it. There is however and exception; each person has an animal that they feel confortable with; they can transform into it at any time without having to see a real example. The hability is passed from generation to generation.
Woof!, which features a kid who Involuntary Shapeshifting changes into a dog at times.
The TV Miniseries version of the Earthsea Trilogy had a story about a wizard who got so obsessed with shapeshifting into a bear that the bear's personality eventually displaced his own, causing him to eat his entire family. The story comes from the first Earthsea novel, "A Wizard of Earthsea", where the bear-wizard is only said to have killed his son.

Tabletop Games

The New World of Darkness sourcebook Skinchangers has options for playable characters using almost every possible variation of this trope, with War Against The Pure and Changing Breeds adding a few more for good measure.
The Old World of Darkness games featured shapeshifting Splats as well.
- Werewolf: The Apocalypse is obviously about werewolves, but also lets you play as were- hyenas, spiders, cats (lions, tigers, leopards, lynxes, etc.), ravens, bears, foxes, crocodiles, alligators, lizards, snakes, coyotes, rats, and sharks. The extinct (unplayable) races are the werebats, wereaurochs, and wereboars.
- Vampire: The Masquerade has three clans with specialized disciplines that allow for animal shapeshifting: the Gangrel have Protean (the typical bats, wolves, and fog, though variations exist); the Followers of Set have Serpentis (guess); and the African bloodline Akunanse have Obomwe, which allows the Kindred to turn into any animal provided she smears her body with its blood (the creature must obviously be big enough to have enough blood for this to be possible).
- Changeling: The Dreaming has the pooka, selkies, commoner hsien, and inuas (a Native American kith). A member of these kiths has one animal form that she can shift into. The pooka and inuas choose one at character creation, while the selkies turn into seals, and each commoner hsien kith has one animal form its members shift into: cats, fish, monkeys, snakes, and badgers (in case you're curious, the noble hsien kiths are based on the 5 Taoist elements)
In White Wolf's other main RPG, Exalted, the Lunar Exalted are able to take the form of any species, so long as they've drunk the heart's blood of a member of that species, and can build up an impressive library of forms this way. They can also apply this to humans, although it works a little differently (each human form they add to their library allows them to take that /specific/ human form).
- It actually works that way for animals too. You are taking that animal's form. It's just that the most common hunt is for one that's an excellent specimen but doesn't stand out. You could, say, hunt an espionage target's favorite dog so you'd be close to him for an extended period.
The Dungeons & Dragons Barbarian-based PrC Bear Warrior is able to transform into a type of bear while they rage.
- And druids can turn into any animal.
- Wizards too, with the right kind of spells. And (like druids) transform other into harmless critters as per the second example of this trope.
In New Horizon, Medeans merge with the genetic code of the native wildlife. Unlike most other examples of this trope, this is permanent... although, oddly, it doesn't effect any kids they have.

Toys

Tha Makuta in Bionicle liked to take on animal forms, most famously Miserix, who preferred reptile forms to his original body (his only existing official image also has him turned into a dragon). The Phantoka Makuta team chose the form of bats, while the Mistika team took on the semblance of insects. However as a subversion, due to a mutagen, they couldn't turn back.

Video Games

Druids in Warcraft III could turn into the totem animal whose demigod they were devoted to.
- Druids in World of Warcraft can turn into various animal shapes. Bear, Cat, Seal, Bird, Tree and an owlbear thing.
- Dragons are also known to have a human form, notable ones being Kalecgos, Alexstraza, and Neltharion (Deathwing as most players know him).
- It's not ALWAYS human. Alextraza and her consert turn into High Elves, Chronomaru turns into a Gnome, Yersa becomes a Night Elf. Goblin and Blood Elf forms have been seen as well for other dragons. Also Deathwing human forms or his human one has changed a lot since his days as Lord Prestor.
  - Deathwing's human Form retains the reforged lower jaw that he has in his dragon form. (See Fridge Horror.)
Druids in Diablo II: Lord of Destruction can acquire the ability to turn into a werewolf, or the slightly-more-exotic werebear.
Most Dragons in Fire Emblem games can transform from one form to the other, with varying degrees of ease. There are a few unique cases because the games all take place in different universes.
- Fire Emblem for the GBA seems to imply that it's quite difficult for dragons to switch from form to form without losing their memories and personalities from their other forms.
  - That could be because one character was forced to undergo their transformation, instead of choosing it voluntarily like any other time.
- Sword of Seals and Sacred Stones both required that your Dragon unit have a stone with a limited number of charges in their possession in order to switch forms.
- Path of Radiance and Radiant Dawn added the Laguz, of which Dragons were one of the many races, who could transform from one form to the other at will, though they would revert to their humanoid state when they ran out of transformation points. A select few characters could stay transformed as long as they willed it, but most of them had their stats cut to make up for it. In Path of Radiance, the Laguz would transform without the player's choice or input when their meters were full, but Radiant Dawn allowed the player to activate it whenever they wanted so long as they had transformation points to use.
In the Banjo-Kazooie series, visiting one of two shaman-type characters (Mumbo-Jumbo in the original and Grunty's Revenge or Humba-Wumba in Tooie) would allow you transform into different things; this is usually an animal (but not always; other transformations have included a tank, a submarine, and a washing machine). Oddly, the main characters are already animals.
The entire premise of the Bloody Roar game series is based on this trope.
Likewise EVO Search for Eden.
Altered Beast has the Werewolf, dragon, bear and tiger forms. Also for the Big Bad, he has a rhinoceros form.
In The Legend of Zelda: Twilight Princess, Link transforms into a wolf. It is initially involuntary due to the Twilight invading Hyrule, then Zant curses Link to make it permanent; eventually, the Master Sword breaks the curse, and Link gains the ability to transform at will. Interestingly, instead of throwing away the gem that cursed Link in the first place, they hold onto it, and apply and remove it using the Master Sword to switch forms.
- In A Link to The Past, entering the Dark World without the protection of the Moon Pearl causes Link to transform into an adorable, defenseless, pink bunny-man. All in all, becoming a wolf was a much better deal.
Solatorobo provides a rare inversion: In a world populated by anthropomorphic dogs and cats, the main character can transform into a human to become more powerful.

Web Comics

In El Goonish Shive, Grace can turn completely into a squirrel.
- Ellen once turned herself into a duplicate of the family cat, "Brownie". She could still talk via magic and retained her mind.

Web Original

Kodotai, Bestiario, Manimal, and Menagerie from the Global Guardians PBEM Universe all have the power to assume the shape of any animal species they want. Russian hero Ursa can turn into a giant brown bear. Indian hero Bagha can turn into a large Bengal tiger.
Limyaael has a rant on shapeshifters, on shapeshifter societies and on blurring the distinction between the "human" part and the "animal part".
In the Whateley Universe, there are Weres who can shift into animal or were-animal forms, plus some mutant Shifters can do it. (Some mutants end up stuck in the involuntary version because of the way their power first manifests.)
Dragore from both Furtopia RPs of Darwin's Soldiers was turned into a dragon for unspecified reasons.
- Professor Sehack from the rebooted Furtopia RP was turned into a Bengal tiger for unspecified reasons.
Qrow Branwen and his sister Raven from RWBY were given the power to turn into a crow and a raven respectively by Ozpin.

Western Animation

Beast Boy from Teen Titans has this as a special power.
- Interestingly, the involuntary subtrope occurs in the episode "Bunny Raven, Or How to Make a Titanimal Disappear". Mumbo the Magician changes the Titans into various animals. Beast Boy is rendered only able to change into inanimate objects, with a lamp as his base form.
- In the comic book, Beast Boy is known as Changeling and while he can't assume giant T-Rex forms without great strain, he is able to speak in any form. This is because he's not limited to shifting into animals, it's just a preferred style.
Jayna of the Wonder Twins from Superfriends. When the twins touched, Zan could turn into some form of water/ice, while Jayna could transform into any sort of animal.
The Monkey Talisman in Jackie Chan Adventures. The owner can turn him/herself or others into any animal they can think of.
Wild Kratts has this as the founding concept, in which the main characters can assume animal shapes using the Applied Phlebotinum in order to get close to the real animals.

Examples of Involuntary Animorphism