Trans Nature

A person is either part of a certain category (such as a certain species or gender) that they do not feel all right with, and so they want to be part of a different category, or the person was assigned a certain category (often against their will) that they never belonged to in the first place, or some combination of both. Because of this, the person may want or need to change their body or nature or both.

In fiction, Trans Nature can take any form, especially in Fantasy and Science Fiction. Note that trying to regain your true form (after having been cursed, for example) does not count. Starting to identify with your new form does, however.

When a character is a fictional kind of Trans Nature, it is often a big part of this character being a hero or villain: Either he's a member of a oppressive/evil group transitioning to become one of the good and/or oppressed people, or we have a "traitor" who identifies with the "wrong" group.

It can also work as an inversion of Internalized Categorism: Bob thinks men/humans are bad, but instead of denying himself the good things about being a man/human or doing bad things because he thinks that this is what being a "real" man/human means, he instead stop being a man/human -- magically changing into something else.

Expect the character to be in a world of trouble if there is No Transhumanism Allowed.

May be caused by Humanity Is Infectious, or inversions thereof. In some cases, Trans Nature leads to Humanity Ensues. Note however that that trope is usually not combined with Trans Nature - instead, the animal resents having been transformed to a human. One very common form of Trans Nature is Pinocchio Syndrome: A robot, living doll or whatever wanting to become a real human.

Supertrope of Transsexual and Pinocchio Syndrome. Sometimes a Sister Trope of Ascend to a Higher Plane of Existence.

Comic Books

 * In Fables, we have the fox Reynard who is attracted to female humans and want to become a human so he can seduce them.
 * We also have some cases of regular Pinocchio Syndrome, with Pinocchio himself and some of the wooden soldiers becoming human.

Film

 * In Avatar,.
 * In Mammoth, our failed Mighty Whitey protagonist falls in love witha thai woman and is quite shocked that she thinks men are better then women and that it's okay because she can be a man in her next life if she is good enough. His wannabe-feminist preaching fails to impress her.

Literature

 * One of Stephanie Plum's nieces wants to be a pony when she grows up.
 * The Merry Gentry series has a number of people who want to be sidhe and often mimic them by dying their hair an unnatural red or getting plastic surgery to get their ears pointed. The later is laughed at by real sidhe because only half breeds have pointed ears.
 * In the Isaac Asimov novella (and later film) The Bicentennial Man the robot "Andrew" desires to be human, so he gets various implants to change his robotic/positronic body & mind into biologic parts. When he finally becomes fully human he gets acknowledged as such by the government,.
 * Averted in the Doctor Who New Adventures novel Original Sin - it's very popular amongst trendy young humans in the 40th century to undergo radical cosmetic surgery that makes you look like an alien ("body bepple"). The Doctor explains that this doesn't mean they actually like aliens; like many empires, the Earth Empire has a fascination with its vassal states' cultures but contempt for the bearers of said culture.
 * In Cornelia Funke's Reckless, the girl referred to as Fox was given the ability to change into a fox after helping a wounded vixen, and much prefers that form to her original human one.
 * Briefly mentioned in Outcast of Redwall; Jodd the hare was raised by squirrels and wishes to be one, to the point that he ties his tail to his ears in the hope of stretching it longer.
 * The Neil Gaiman short story "Changes" has elements of this. A drug designed to cure cancer has the "side effect" of completely changing a person's biological sex. A biological female who takes the drug will become a biological male and vice versa. It's mentioned that the drug has made sex-change operations obsolete, though some people take it to recreationally change sex.
 * In Reaper Man, the soon-to-be-dying wizard Windle Poons says at his Going-Away Party that he's considering being reincarnated as a woman. His colleagues are a little bit taken aback.
 * The Librarian, of course, is perfectly content to remain an ape, even if his transformation from a human wasn't actually by choice. Colleagues who'd known him before are now of the opinion that he was always an orangutan deep down, he'd just started out looking human due to an accident of birth.
 * Discworld dwarfs are facing a kind of cultural revolution of a trans natured kind. Most of dwarf culture centres around stereotypically masculine things, like armour, weapons, drinking and mining. All dwarfs dressed the same, grew their beards long and used male pronouns for themselves. Most of dwarf "sexuality" consisted of finding out what physical sex your boyfriend was before you got married, not that it would change anything. But recently, some dwarfs have been daring to be more feminine. No shaving, obviously, but maybe wearing very slightly lighter chainmail, or a shinier axe. Maybe even lipstick or a chainmail skirt. Of course, since dwarf gender is so optional, it still doesn't mean that they necessarily do have female body parts. Just that they choose to be perceived that way.
 * Captain Carrot Ironfounderson, as evidenced by his name, is a dwarf. He is also, through accident of birth, a six-foot tall human king. But he sees no reason why that should stop him being a dwarf, just like adoptive Dads. Nor does he see why some funny crown birthmark, fancy sword and "royal ancestry" should make him have to be King of Ankh Morpork. He would much rather work his way up the ranks of the Ankh Morpork City Watch by the sweat of his brow. This species dysphoria may be what helps him understand Angua, his werewolf girlfriend.
 * Speaking of Angua, Discworld werewolves are notably not "human most of the time". They are always a werewolf. They just happen to be human-shaped a lot of the time and wolf-shaped at least some of the time. Meanwhile, Wolfmen are the same but the opposite way around. Many werewolves/wolfmen have problems changing shape, in fact. Some can only change in the moonlight, or not at all, as evidenced by Angua's sister, who could not change into a wolflike shape, and one of her brothers who cannot change into a humanlike shape but chose to pass as a champion sheepdog in Lancre. Apparently werewolves and wolfmen are simply two different examples of the same species (which can interbreed with human and canine biology).

Live Action TV

 * In both continuities of V, alien lizards are evil. Those lizards who side with humanity stop having a real lizard mind, instead developing human personalities/emotions.
 * In Star Trek: Deep Space Nine, at least two episodes are about regular humanoid Trill wanting to transition to become "Joined Trill". A Joined Trill is a composite species, with one humanoid component (normally from the Trill race, though a human was briefly joined in one TNG episode) and one symbiont. Becoming a Joined Trill brings on many changes, including a form of reincarnation: You retroactively gain past lives in the form of the symbiont's former hosts and their memories, and after your death you will continue to live on as one of these past lives for subsequent hosts.
 * Trill must be trained and prepared for a long time before Joining, if they are good enough to be selected, or they may become a person that is far more like past host personalities than the current host's previous personality. Will Riker, who had no idea what symbiosis was like at all, was entirely submerged without realising that there was any alternative. Ezri Tigan, a humanoid Trill who was forced into Joining by circumstance, had at least grown up in a Trill culture and Ezri Dax kept most of her personality.
 * In Star Trek: Voyager, the AI called "The Doctor" as well as the former Borg drone Seven Of Nine are both transitioning. Unlike their predecessor Data from TNG, however, they do not want to become humans. Instead, they are trying to grow into something new, despite the Captain's bias towards the concept of their "humanity" being developed.

Real Life

 * A general real life example: Otherkin. To quote Wiki Fur, "Otherkin are those who believe that their physical forms do not define or fully encompass their mental states, personality, psychology, or spiritual nature." See the full article here.
 * And some furries as well. These most often take the route of reincarnation much like the aforementioned religions.

Tabletop Games

 * In Shadowrun, elves are a subrace of humanity. Some normal humans are "elf wannabees" who want to be elves, and sometimes use plastic surgery to make themselves more elf-like. They're usually looked down upon by real elves.
 * In Feng Shui, the Ascended are an Ancient Conspiracy of intelligent animals who used magic to become human, and then took over the world to prevent the same magic from being used to return them to animal form.

Web Comics

 * Reynard the Fox also appears in Gunnerkrigg Court, and true to the myth, he fell in love with a human woman. Rather than shapeshifting, however, he convinced Coyote to grant him the power to possess anything with eyes--and he uses it to take the body of a young human male so he can go to the court and woo his beloved...
 * There is a Test that, if taken and passed, allows the test-ee to abandon their old nature and become something new. Humans can become animals and move to Gillitie (like the Kershaw family did), while animals and fantasy creatures can become humans and move to the Court (like Red and Blue did).
 * El Goonish Shive features regular genderswapping with the aid of magic and a superscience transformation gun.
 * Averted by Justin, who dislikes being temporarily female at a transgender birthday party.
 * Averted by Sarah, who enjoys being temporarily male for the party, but is otherwise female.
 * Possibly played straight by Susan. Her time as a male apparently felt little different to being female, to her surprise. She also trades uniforms with Tedd, because their school has gender-specific uniforms and they both prefer the opposing gender uniform.
 * Played with by Tedd, whose androgynous looks cause people to assume that he is a girl anyway. He developed the genderswapping features on the transformation gun just so that he could actually switch back and forth whenever he wanted to, but mostly because he's a Chivalrous Pervert and proud of it.
 * Subverted by Grace. She has shapeshifting powers anyway and her sense of self has absolutely no ties to outer appearance in any way.
 * Played straight to the hilt by Ellen & Elliot! At first, Elliot was Tedd's much more obviously male friend. He also started off normal to counter Tedd's "Mad Scientist" theme, though that soon got replaced with a Magic Versus Science theme when he was revealed to be skilled at "Anime Style Martial Arts" including projecting spells from his hands. He gets hit by the "Venus" transformation (becoming an extremely attractive, long-haired girl for a month), he demands that Tedd get him a quicker cure (so as to avoid going to high school with an attractive girl's body for a month). Tedd finds out about a crystal that gets rid of transformative "curses", which should work, since the gun is based on alien Magitech. They find the crystal and Elliot touches it.
 * Long story short, it split him into two people. "Elliot" who got to keep his name (because he was the male one) gained a hand-beam spell to give people the "Venus" transformation but now has to burn off his excess magical energy once a day by spending a few hours as a woman. "Ellen", who was created from the "curse" that was removed, is permanently a woman now, and only slowly coming to terms with the thought that she might be okay with that. But she still remembers having been a man, mind and body, all her life as well as not being able to date Sarah, the girl she remembers as her girlfriend. She also has the ability to use the anime martial arts but has decided to pursue magic more in order to differentiate herself from Elliot, although she really likes to use her own "Venus" transformation on him.

Western Animation
"Doctor (on negroplasty) It's a fairly common procedure, really. Just the reverse of a caucasioplasty just like Michael Jackson had."
 * In The Boondocks, When Uncle Ruckus die, he will finally become a real white man in the heaven for white racists.
 * King Louis from The Jungle Book, an ape wanting to become a human.
 * Another Louis, the alligator from The Princess and the Frog, wants to be human so that he can play trumpet in a jazz band.
 * In the Disney version of The Little Mermaid, Princess Ariel of the Mer-people have a fixation with humans, eventually falling in love with a human and becoming one herself. In this version of the story, humans and mer-people are portrayed as equal, so Ariel's transformation isn't about becoming better or worse.
 * The original HC Andersen version is not so nice. In this version, it turns out that God love only mankind, so the Mermaid is doomed from the beginning simply for being born as a "lesser" species. Since her quest in this version was limited to trying to reach out to her Love Interest, it's not an example of this trope. Oh, and it fails miserably, too.
 * Teachers Pet is about a dog who wants to be a boy.
 * The South Park episode "Mr. Garrison's Fancy New Vagina" is about this trope, focusing not only on the title character, but on  Mr. Garrison gets a "vaginoplasty" to become a woman,   gets a "dolphinoplasty" to become a dolphin, and   gets a "negroplasty" to become tall and black. In the end, Mr. Garrison wanted a "peniplasty" to become a man again after realising that he's "just a guy with a mutilated penis". However, his genitalia was used for surgically altering , and  , leaving Mr. Garrison as a woman until he grew new genitalia on a mouse.


 * Afterwards, in the case of, this was never mentioned again.

Real Life

 * There are several versions. For example, trans people are coercively assigned a certain gender at birth that does not match their real gender or are simply born in a gender that doesn't match them. There are also religious examples, mostly tied to belief in reincarnation -- since men have higher social status, many Hindu and Buddhist women openly hope to be male in the next life, while still having an entirely female gender identity in this life.