Involuntary Shapeshifting / Anime & Manga

• The five protagonists in Ame Nochi Hare will transform into girls whenever it rains.
• 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 Ordinary High-School Student persona, he's not nearly so hideous) he is outfitted with a veritable arsenal of 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.
• Atsushi in Bungo Stray Dogs used to turn into a white tiger involuntarily whenever he was under the moon. With the help of Fukuzawa he is able to transform by his own will.
• Ryu Sugiura from the OVA "Call Me Tonight" is a teenager who is infected with a curse that causes him to transform into a different monster every time he is sexually aroused.
• In Akira Toriyama's manga Doctor Slump, Chinese immigrant Tsun Tsuku-tsun inexplicably turns into a tiger when he comes into contact with a girl, and turns back human when a boy touches him.
• Dragon Ball character Lunch (Launch in the American dub) changed personalities (and hairstyles) whenever she sneezed. The blue hair represents her Nice Girl form, while her blond-hair gives her a Hair-Trigger Temper (with guns!).
  • 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. Of course, they are 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, making him unaware that it was he who killed his grandfather, apparently because of infant brain damage from when his spaceship crashed.
• Inukai from Flying Witch, 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.
• Several members of the Sohma clan in Fruits Basket, due to a curse that has twelve of them turn into an animal from the Eastern Zodiac whenever they're hugged by someone of the opposite sex who isn't cursed, or when they're physically weakened. The Sohma who represents the Cat (an animal who would have become part of the Zodiac if the Rat hadn't tricked it) has a second, monstrous form and must wear prayer beads as a Power Limiter to appear human. While they can voluntarily transform by willingly hugging someone who isn't cursed, it's still risky to do so since the curse will be discovered. Most of the time their transformations are unpredictable, so they have to be careful.
• This also applies to the half-demon Izumo/Gyu-oh to from the anime Inuyasha. During the day he looks like a pure human, but at night he looks like a pure demon.
  • In fact, all hanyou (half-demons) in Inuyasha have a time where they become completely human. Inuyasha himself becomes human on the night of the new moon.
• The Junji Ito Kyoufu Manga Collection story "Face Thief", like all of Junji Ito's works, takes this trope and dives headfirst into a pool of Nightmare Fuel 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. The end result is not pretty.
• Kaiju Girl Caramelise deals with Kuroe Akaishi, who sees parts of her body transform in freakish ways ranging from a scaly reptilian hand to spikes along her spine whenever she experiences strong emotion. She tries to avoid this by acting as a loner, but her burgeoning feelings for classmate Arata Minami leads to her emotions kicking into overdrive and her sporadically turning into a Kaiju.
• Kanon has an animal to human one in Makoto. Which gets revisited in CLANNAD with Shima, with all the Tear Jerking drama that comes with it.
• Protagonist Kate Menella from Love Is in the Bag turns into a bag whenever she gets excited over something.
• My Monster Secret: Shiho is half werewolf, meaning she transforms into a wolfman (literally; she turns into a Little Bit Beastly male with his own personality) whenever she sees the moon. Or a photo of the moon. Or even a drawing of the moon.
• Negi of Negima! Magister Negi Magi has been in the process of transforming into a demon ever since he started using 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.
• Yayori from Neko-de Gomen! has little control over when she has cat ears and tail and when she doesn't.
• This is done several times in Pokémon.
  • Castform changes shape depending on the weather.
  • In the Pokémon Adventures 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.
  • 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.
• Princess Tutu: Princess Kraehe's Transformation Sequence; her Secret Identity 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.
• The second season of Rage of Bahamut: Genesis has Nina, an energetic teenage girl who transforms into a powerful red dragon whenever a handsome man makes her heart race. Leads to both hilarity as Nina struggles to control her emotions in front of men and drama when Nina finds she wants to transform, but can't because of the limitations of her ability.
• Ranma ½ has the iconic cursed springs of the remote valley of Jusenkyo. Once a person is immersed in a spring, they are cursed to transform into a creature based on which of the specific springs they fell into whenever they are splashed with cold water, with only the touch of hot water reverting them to normal. Though this makes the curse easy to invoke on the rare occasions it's desired, it's far easier for it to be invoked in unwanted situations.
• Reincarnated As The Strongest Wand has Reiji, stuck as a wand most of the time. In certain specific situations, he will transform into a human, whether he wants to or not.
• In Adolescence of Utena, Utena and Shiori turn into cars, for reasons that only make sense if you read the plot as an allegory. Nanami also turns into a cow (or at least thinks she does) in both the regular series and the movie.
• In The Seven Deadly Sins, King, a fairy, sometimes shape shifts into his human form as a form of his expression in any given situation.
• Ren/Run in To Love Ru. 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 force herself to sneeze when one of her plans (usually to embarrass Lala in front of everyone) fails, making it a not-so-Involuntary Shapeshifting.
• On Tokyo Mew Mew, 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 becomes an actual kitten.
• Urusei Yatsura has Rei, the green-haired space bishonen 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.

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