Sex Shifter

Some species, mostly fish, amphibians, and invertebrates, are capable of changing sexes under certain circumstances. In fiction it is sometimes possible for other creatures, even humans in some cases, to do this as well (and often much faster).

Subtrope of Gender Bender. May involve Bizarre Alien Sexes. Usually a part of any story in which Shapeshifters Do It for a Change.

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Examples:

Anime & Manga

• Black Butler: Ash Landers and Angela Blanc are revealed to be the same character shifting sex. They have somewhat different personalities though.
• The eponymous junior high school boy of Futaba-kun Change! becomes a girl whenever he becomes sexually aroused and changes back some arbitrary amount of time after his arousal passes. This runs in his family; the man Futaba always believed to be his father actually gave birth to him, whilst his sister exploits her male form to bed a string of women. It's ultimately explained that their family has this ability because they're descendants of a stranded race of Human Aliens for whom this is normal. And it turns out Futaba's love interest is actually a distant relative, so they awaken this ability in her so she and Futaba can always be together. Also, the trait is true-breeding, and thanks to Futaba's sister/brother Futana being a super-hot playboy who shamelessly leaves a string of bastards in her wake, it's implied that eventually the whole world will become just like this.
• Hell's Paradise: Jigokuraku: The Tensens, being Plant People created to achieve perfection, can shift between male ("yang") and female ("yin") forms.
• One Piece: Emporio Ivankov ate the Horm-Horm Fruit which allows him to inject hormones from his fingertips. Its many applications include "male/female hormones" which can turn himself or any recipient into the opposite sex.
• Iori/Shiori of Osananajimi wa Onnanoko ni Naare is a functional sex-shifter: The fairy Sylphie turns them from their original male form (Iori) to a female one (Shiori) as often as possible, intending the change to be permanent, but they're Resistant to Magic enough to prevent or reverse it by insisting they're male regardless. But Shiori has to be confident while saying so, thus undermining her masculinity (usually by making her conscious of her female body) causes a Shapeshifter Mode Lock, which Sylphie tries to exploit.
• Ranma ½: Because of the specific Jusenkyō curse, Ranma Saotome can change between genders, turning into a girl when cold water is splashed on him, and changing back when hot water is splashed on her. Prince Herb of the Musk Dynasty, the central antagonist of a late-series arc, is unique in that he suffers from the same curse.
• Science Ninja Team Gatchaman one of the show's most famous plot twists involves Berg Katse, the second-in-command of the Galactor organization. It eventually turns out that not only is "he" the same person as a recurring female Galactor commander, but is also a sex changing mutant created by Leader X fusing two fraternal twins in the womb. Though unable to control it in their youth, Berg Katse has complete control of this power by the time of the series proper.

Comic Books

• Apex from Avengers Arena is an interesting case. She shares her body with her brother and their body shifts gender depending on who is in control.
• The Eternals can change their appearance, including their sex, when the great machine resets and resurrects them. Many of them choose to do this fairly often by Eternal standards - every 20 to 25,000 years or so.
• Fine Print: All the Cubi and Cupids can instantly change their sexes as they'd like.
• One of the many magic keys from Locke & Key allows a person to switch from male to female by walking through a door in Keyhouse. Known as the Gender Key, it was initially used by one of the Locke ancestors to participate in the American Revolution as a more extensive version of a Sweet Polly Oliver. In the 20th century, Duncan Locke liked to use it for fun when he was a child, much to the exasperation of Rendell and his friends. And then it ended up in the hands of Dodge AKA the Well Lady, and the rest was history...
• Loki, as a shapeshifter can take any human form, male or female. Seen most notably in his own series, Loki: Agent of Asgard, though it's come around much more often in other comics featuring them.
• The shapeshifting Skrulls of the Marvel Universe can change their sex as well as their appearance. For example, in Runaways, Karolina turns out to be engaged to Super Skrull-in-training Xavin thanks to her parents' actions. She objects not because she isn't sold on the marriage (since it's the only way to stop a war between their species), but because Xavin's male and she's a lesbian, so Xavin solves the issue by showing her that they can take a female form. They end up switching between male and female form for all their appearances afterwards.
• Wonder Woman (1987): Kreel are able to shift their physical sex when they reach a certain age, which was how they reproduced when entire generations were born male or female in the past. Being (openly) female is illegal in the Sangtee Empire (until the rebellion lead by WW is successful) and reproduction is now done by cloning, allowing the government to control the population. To the Empire's annoyance their natural ability to shift means cloning a man can result in a female infant.

Fan Works

• Child of the Storm has Loki capable of this, both when there's a 'need' for it (i.e. when it's convenient), and when he feels like it. Word of God is that he's primarily male-presenting and male-form-preferring, but he's fundamentally fluid.
• In Harry and the Shipgirls, both Inari Ōkami and their sword Kogitsune-Maru's avatar are prone to changing between a male and female form on a whim.
• The Mountain Andthe Wolf: The Wolf keeps a Slaaneshi hermaphrodite named Bjarnhilda (handsome man on one side, beautiful woman on the other) on his crew, capable not only of shifting from one gender to the other but even mimicking other people's appearance (and casting a spell to give other people someone else's appearance).
• Inari in Son of the Western Sea, the husband/wife of Uke Mochi who takes the gods' ability to change their appearances to the logical extreme and regularly changes gender, reflecting how Inari is thought of as different genders in different areas of Japan.
• Ryoga Hibiki decides to undergo a magical procedure to "replace" his Jusenkyo Spring of Drowned Pig curse with a Spring of Drowned Girl curse in Voyages of the Wild Sea Horse, having decided that turning into a girl is far less of a life-threatening hassle than turning into a small pig.
• Vow of Nudity: An elven slave in one story has the Blessing of Corellon, meaning he can shapeshift into a female form (or back) once per long rest. Spectra, as a changeling, can also do this and far more.

Film — Live-Action

• The Tim Daly/Sean Young film Dr. Jekyll & Ms. Hyde takes the old Jekyll-and-Hyde story to another level by making Jekyll male and Hyde female.
• Jurassic Park (1993): Alan Grant discovers the dinosaurs were able to get around the genetic manipulations that made them all female, and theorizes that the frog DNA used to complete their genomes allowed some of them to change sex to male. This handwave has since fallen victim to Science Marches On: parthenogenetic births have been discovered among several animal groups in the archosaur clade (to which dinosaurs are believed to have belonged, as do birds, lizards, and crocodilians), so it's possible that the dinosaurs could have overcome the limitation even with their OEM genomes.
• In Zerophilia, a person with an extra Z chromosome will change gender after an orgasm. By having sex with another zerophiliac, he/she will be Mode Locked into the opposite gender than what he/she was before then. The movie follows a boy named Luke, who has this condition and goes by the name Luca as a girl, pretending to be his own cousin. He/she eventually gets tricked into being stuck as Luca. Fortunately, his girlfriend Michelle and her brother Max are actually the same person, so their relationship works out.

Literature

• In F.M. Busby's The Breeds of Man geneticists searching for a cure to an infertility plague caused by an AIDS cure Gone Horribly Wrong accidentally turn some people into serial hermaphrodites that alternate between male and female monthly based on menstruation.
• In C. J. Cherryh's Chanur Novels stsho are somewhat prone to "phasing" with little warning, assuming a new gender and personality.
• In N. K. Jemisin's Inheritance Trilogy, the God of Chaos Nahadoth uses human manifestations of all genders and has had children in a variety of reproductive roles. The distinctions are fairly academic to a being whose true form is infinite, inchoate primordial darkness.
• Jurassic Park (1990): Alan Grant discovers the dinosaurs were able to get around the genetic manipulations that made them all female, and theorizes that the frog DNA used to complete their genomes allowed some of them to change sex to male. This handwave has since fallen victim to Science Marches On: parthenogenetic births have been discovered among several animal groups in the archosaur clade (to which dinosaurs are believed to have belonged, as do birds, lizards, and crocodilians), so it's possible that the dinosaurs could have overcome the limitation even with their OEM genomes.
• In The Kharkanas Trilogy, the prequel to the Malazan Book of the Fallen, it is revealed that Elder God K'rul is able to change his sex at will, and does so every other century or so whenever he feels like having a change. He also can and did become pregnant at least once. It's not too surprising as all Azathanai are shapeshifters but K'rul seems to be the only one able and/or willing to shift between sexes.
• The Left Hand of Darkness has a planet where the human-descended inhabitants are asexual most of the time, except when they're in "kemmer" and become either men or women, as well as very lustful.
• Alex Fierro in Magnus Chase and the Gods of Asgard will shift randomly between genders, it comes with territory of having Loki as your mother.
• In Mistborn, a Kandra's physical form depends on the bones that they're wearing. They have some degree of control, as illustrated by TenSoon guessing at the form of a set of bones he's never worn before (the surprise of the Kandra who gave him the bones). Despite this, Kandra characters have a consistent pronoun attached to them, whether their current body conforms to it or not. Kandra also create "true bodies," made of materials like wood or crystal, and sometimes with structures that would be exceptional or even impossible for human bones. MeLaan is shown using her true body to switch between male and female on the fly.
• In Simon R. Green's Nightside works, Jacqueline Hyde is a descendant of Dr. Jekyll who used her ancestor's formula too much, periodically transforming into Mr. Hyde. Jacqueline and Hyde are deeply in love but can never meet directly.
• Virginia Woolf's Orlando more or less spontaneously turned into a woman. The League of Extraordinary Gentlemen's reinterpretation has that happen every few years, owing to his/her father Tiresias.
• In the Patternist series, especially in Wild Seed, the immortal healer Anyanwu is able to change her body at will, which not only includes shapeshifting into animals but also changing sex. The change is so complete, she can even sire children when in a male body, although they're only girls unless she copies the DNA of another male, in which case the resulting sons will be genetically that other man's rather than Anyanwu's. Most of the time, Anyanwu uses that ability to hide from witch hunters.
• Reign of the Seven Spellblades: Volume 2 reveals main cast member Pete Reston to be a "reversi", a mage with the ability to swap sexes. This has some technical advantages such as allowing him to use his uterus as additional magical storage when in female form, and immunizing him to Ophelia Salvadori's Perfume when he switches to female while unconscious after she kidnaps him in male form. Pete doesn't have full control of it and is prone to switching in his sleep.
• One of Neil Gaiman's short stories in the Smoke and Mirrors anthology concerns the massive paradigm shift that society undergoes when an experimental gene therapy intended to treat cancer has the unexpected side effect of performing an overnight and totally reversible Gender Bender.
• In M.C.A. Hogarth's Tales of the Jokka, Jokka can change genders at two points in their life, once in the first seven years of their life and again in the second seven. Some never Turn, others Turn once, some Turn then Turn back to their original gender, and a few rare individuals have the chance to be all three sexes.
• Noel "Double Helix" Matthews in Wild Cards. Born intersexed, they (well, he prefers "he") gained the ability to change between fully male and fully female. This actually allows a small degree of Humanshifting, possibly by altering the precise balance of hormones. As a bonus, he can teleport, but only during the day in a male form and only at night in a female form.

Live-Action TV

• A notorious convention anecdote in relation to Babylon 5 has J. Michael Straczynski responding to all the Ho Yay fan reaction to Londo and G'Kar by distributing a joke script to the actors in which G'Kar changed sex to become female, revealing that Narn are biologically capable of doing it as a response to being in an unduly one-gender environment, and promptly tried to seduce Londo, while still being played by Andreas Katsulis. The actors were apparently entirely enthusiastic about it.
• Doctor Who:
  • The 21st-century version has explicitly confirmed that Time Lords sometimes change sex on regeneration, although fans had speculated about the possibility for decades and it had never been explicitly ruled out. The sex change usually comes with a gender change as well.
    • The Master, a male villain, regenerates into the Mistress (Missy, for short), making her first appearance in series 8. Despite the misogyny of her previous incarnation, Missy doesn't seem to mind this change one bit, as she goes around wearing a fancy Victorian dress, heavy makeup, and insists on being called a Time Lady instead of a Time Lord.
      Missy: Some of us can afford the upgrade.
    • The white male General regenerates into a black woman in "Hell Bent". Not only that, her dialogue indicates that all of the incarnations before the male General have been female as well.
    • The Doctor finally gets their turn in "Twice Upon a Time", as they regenerate into a woman in their thirteenth incarnation. Unlike Missy, though, she seems to go with a more androgynous look. Then again, she doesn't really seem to mind either, as her response to seeing her own reflection for the first time shows.
      The Thirteenth Doctor: [grinning] Oh, brilliant!
  • "The Hand of Fear" shows a Kastrian regenerating from female to male, and being surprised that the Doctor is surprised by it, as he should know all about regeneration.
• Gen V: Jordan Li can shift between male and female forms which have different powers. This is also tied to their identity, as they are bigender.
• The Monster of the Week in the Grimm season 4 episode "Double Date" is a member of a worm-like Wesen species that can change gender at will. It becomes clear that each gender has its own personality, but they live together symbiotically. Oddly Truth in Television, as blood flukes actually live like this.
• In From the Cold: Anya can take on a male form due to her body-morphing ability temporarily.
• Misfits: Curtis gets this as his second power, having the ability to become a female version of himself at will, who he names Melissa.
• Mork from Mork & Mindy states that Orkans' "parts are interchangeable".
• A newly introduced mermaid-tribe from Siren are all born female, but are able to transition to male in order to reproduce by going in a specific pool.
• The Monster of the Week in The X-Files episode aptly titled "Gender Bender" is a member of an (apparently) alien humanoid species whose biological gender changes every time after they have sex.

Music

• In Blue Öyster Cult's Imaginos and its sequel, the titular shapeshifting Villain Protagonist often shifts his sex to take on the female persona of "Desdinova", who narrates at least two of the first album's songs.

Mythology and Religion

• Succubi and Incubi are often thought of as the same being, just shifted into a different sex. The usual modus operandi they're given is that a Succubus seduces a human man for his genetic material, then transforms into an Incubus to seduce a human woman and impregnate her with said genetic material. This leads to the woman having a demonic baby... somehow...

Podcasts

• In Metamor City people with the androgyne variation of the curse can change sex at will, though they need to spend more time as the opposite gender that they were born with. Considering that the original version of the curse was a one-way Gender Bender.

Tabletop Games

• Æon:
  • The Qin are small slug-like aliens who regularly switch sexes.
  • Any Psion with enough Biokinesis can modify apparent gender and then their physical sex as a matter of course.
• Dungeons & Dragons:
  • In 5^th Edition:
    • Some elves have the power to change their sex and gender over a long rest, which is named "Corellon's Blessing" after their genderfluid patron god. It's rare enough to require DM approval for a given Player Character to have it, but has no mechanical effect in gameplay.
    • Kobolds will spontaneously change sex if there's a severe imbalance in the male to female ratio of a warren as a result of casualties inflicted by monsters or adventurers. As kobolds are egg-laying reptilian humanoids who lack any sexual dimorphism, this is not something that they consider a big deal beyond the way it helps their species survive in a hostile world.
  • Succubi have been able to do this since at least the third edition of the game through their Humanshifting powers, all the better to lead mortals into temptation.
  • In the Forgotten Realms setting, in older lore, the rare male clerics of Eilistraee, Goddess of Redeemed Drow, were said to need to regularly transform into women in order to maintain access to their holy magic. This lore was dropped in 3^rd edition onwards for certain Unfortunate Implications.
  • Verdan, a race of Chaos-warped goblinoids originating from Acquisitions Incorporated, are known to sporadically and randomly shift genders, with the implication that every verdan does so at least once in its lifespan. As a result, the verdan culture has no innate gender-specific roles or traits.
  • Gobowins, from the Wicked Fantasy setting, are also a goblinoid race known to randomly shift genders throughout their lives. It's one of the traits that makes them Explosive Breeders.
  • Changelings, from Eberron, have this ability. Unlike their Doppelganger relatives (the exact relation is uncertain), they do have a "true" sex, but their shapeshifting allows them to take other sexes (male, female, both, neither) and is powerful enough that they are fully functional, including allowing pregnancy. Their willingness to do so varies — in terms of the common Changeling philosophies, Becomers happily jump gender as much as they jump species, Seekers are usually closest to this trope (they are more willing to change sex than change race from the true Changeling appearance), while Passers seek to stick to a single assumed form which may not correspond to their "true" sex.
• Changelings in Eberron are born asexual, develop their proper gender in early puberty, and then become capable of fully shifting sexes when their powers fully mature in mid-puberty.
• Eclipse Phase has a "sex switch" BioMod that enables one to do this (and comes standard with Pleasure Pods), though the process takes a week.
• One of the tricks available for Lunars in Exalted. Their patron god-goddess-whatever-it-feels-like-today Luna does so on a regular basis, including appearing as a pregnant man on occasion.
• In GURPS "Hermaphromorph", from GURPS Bio-Tech is a five-point trait that allows a character to do this.
• In Kitsune: Of Foxes and Fools, the kitsune Hayaku can change genders at will, for free at the beginning of each turn and by spending one foxfire any other phase. Fellow kitsunes Saski and Sareiko once had a competition to see who could seduce Hayaku first; the result was that Saski impregnated Hayaku with the twins Ai & Midori, while Hayako knocked up Sareiko with Seiki.
• In Munchkin, the 'Freudian Slipper' allows the user to change sex (in-game, obviously) whenever it suits them most. If they lose the slipper and they're not their (real-life) biological sex, however, the former user is at a disadvantage in their next combat as normal for Sex Change Curses.
• The New World of Darkness:
  • Vampire: The Requiem: The Galloi bloodline can transform themselves and others into the opposite sex with a ritual Blood Bath. The effect normally wears off, but if the transformed person permanently invests some Heroic Willpower into the change, it becomes permanent.
  • Mage: The Awakening:
    • Any Mage who's trained in Life magic can temporarily transform themselves or another person into the opposite sex. A prose interlude in one Sourcebook has a mage chew one of their peers out for trying to determine magically whether they're Transgender since it's incredibly rude to pry.
    • The Daksha Prestige Class can switch at will between male, female, and hermaphrodite versions of their original form, which they see as a manifestation of the Enlightenment Superpowers that will help them usher in a new Golden Age.
• Teenagers from Outer Space: Aliens with the Boy/Girl/Boy power can change sex at will.
• In Unknown Armies, Avatars pursuing the Archtypes of the Mystic Hermaphrodite and the Freak both gain the ability to voluntarily change their sexes at will at higher levels of embodiment.

Video Games

• The Black Heart: Animus, the twisted child of Elizabeth Bathory and Final. Among his quirks is that he often changes genders during fights. Male!Animus tends to act more brutal and animalistic while Female!Animus acts more between the cross of a ballerina and a sex maniac, but in both forms he's prone to laughing and using rusty metal as a weapon to hurt both the oponent and himself.
• In Fate/Grand Order, Chevalier d'Eon's fame for disguising as the opposite sex, crossdressing in general, and/or being just that androgynous in life gives their Heroic Spirit this specific ability as a function of their Self-Suggestion personal skill (in gameplay it just heals them and clears debuffs).
• League of Legends has Neeko, the Curious Chameleon, who has the ability to mimic other people at will, and gender is no object for this, though she generally thinks that male sho'ma feels strange and takes getting used to.
  (shapeshifting into a male champion) "Do I smell as bad as I look? (sniffs) Yes."
• Runescape: The Makeover Mage Pete/Peta frequently changes their own sex with the same magic they use to perform Gender Benders for player characters.

Visual Novels

• In the Wolf Hall entry of the Magical Diary series, Blaise is a member of a magical species who can change back and forth between male and female depending on mood.

Webcomics

• Bud, in 1977:The Comic has an encounter with a bad-tempered Mystical Frog and is everafter cursed with transforming into a woman, his alter-ego Budette, whenever his Berserk Button is pressed.
• The Daily Chaldea version of Ritsuka Fujimaru has been changing gender for so long they no longer remember what their original gender was (#574). Their family studied shapeshifting in hopes of Power Copying phantasmal creatures and failed, leaving this as their specialty (#649). It has the Required Secondary Powers of transforming their clothes.
• Incubi and succubi have shapeshifting powers in Amber Panyko Williams' Dan and Mab's Furry Adventures universe. This includes gender changing at will, though it takes much time and practice to do well. Abel Rewanz demonstrates the boy-to-girl morphing in strip #690, and again in strip #1038, much to Daniel's chagrin.
• Alchemy the reaper from Dangerously Chloe is an Anthropomorphic Personification of Death and doesn't have a gender as such, instead appearing as "Al" (male), "Kimmy" (female), or as a classic skull-faced Grim Reaper depending upon what the soon-to-die person expects to see. Otherwise their gender depends upon how masculine or feminine they're feeling.
• El Goonish Shive: Grace can do this easily as part of her general shapeshifting power, though she typically sticks to being female. Later in the comic, Tedd gains a magic mark that lets him alter his sex at will... which everyone notes is incredibly redundant since he had the technology to do that anyway and frequently made use of it. Also, because of an improper magical awakening and excessive buildup of magic energy, Elliot not only ends up with multiple spells that let him turn into a girl but he needs to turn into a girl regularly or else he might transform without meaning to.
• The artificial lifeform Penelope from Ben Nu~nez's Just Another Web Comic was built as a sentient sex toy by Mad Scientist Eryl Keydon. Penelope can change gender and species on command, though she seems most comfortable as a female feline. See volume 2, page 32 where Penelope recites her tech specs, though be advised: this web comic is patently Unsafe For Work.
• Team RAIN: Viorel Braith is genderfluid and their Semblance allows them to shapeshift into either a male or female form. They'll often be seen doing so even within the span of a single page. Their sister Viola is unsure of which one they were born as, but Viorel doesn't really care either way.

Web Original

• In the Chakona Space universe skunktaurs, a sister project to the chakats, can switch between male and female at will. Though they also have an annual cycle that forces a sex change.
• Whateley Universe has a few, naturally enough, with Heyoka, Reach, Fling, Jimmy T., Chimera, Pounce, and (in the Gen 2 stories) Reinforce, Bewitched, and Ping-Pong being the main examples. However, most of these cases have some degree of Blessed with Suck to them: Heyoka changes uncontrollably depending on the spirits which s/he bonds with, Jimmy T. has trouble controlling who (or what) s/he shifts into while asleep, Chimera is actually two Half-Identical Twins sharing a single body, Reach shifts on a semi-random basis every two weeks or so, Pounce has to be a Cat Girl for several hours each week or suffer painful side effects, Reinforce gets a temporary Shapeshifter Mode Lock if he shifts too many times in rapid succession, Bewitched has drastic personality shifts when female which their male form hates, and Ping-Pong switches form uncontrollably when sexually aroused. Perhaps the one who has it worst is Fling, who changes both physically and psychologically in response to lust, becoming whomever the person s/he's nearest to most desires, which can really suck if that person wants a bimbo, or worse, is a sadist.

Western Animation

• Kaeloo: Word of God is that due to being a frog, Kaeloo can change her sex.

Real Life

• In biology this is called "sequential hermaphroditism" (or dichogamy in botany) and has been observed in many species of invertebrate, fish, and frog. Even some plants are capable of this.

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