In stories where characters' bodies can be altered through Shapeshifting either voluntary or not, a common requirement for such a transformation is directly exchanging a particular physical attribute with someone else who already has that attribute. This is usually based on some in-universe version of Equivalent Exchange that also explains away Shapeshifter Baggage.
Such trait swapping may involve entire discrete limbs being traded, perhaps in a LEGO Body Parts manner. Other times, the swap involves a more general and/or abstract trait such as height, weight, musculature, skin complexion, or age. More fantastical works may even have two characters changing into each other's species while still recognizably being themselves.
In action-focused works, the characters will likely swap whatever traits will give them an advantage in battle, such as switching with a stronger character's muscles for greater offense or switching with an iron-hided character's carapace for greater defense. More prosaic comedies and dramas instead tend to pair this with characters who want to look more attractive, such as a character with Height Angst stealing the desired height from someone taller or a fat person with Weight Woe transferring the weight to someone thinner. Also, kids who want an Overnight Age-Up may steal the age from adults who get younger as a result, while an Immortality Seeker may steal the youth from someone who undergoes Rapid Aging in response.
This trope can be thought of as "Freaky Friday" Flip meets Partial Transformation. Indeed, the boundary between this and "Freaky Friday" Flip can be blurry if two characters swap enough traits to be mistaken for the other — and the number of traits that need to be swapped for that to happen can be low in certain illustrated and animated works where characters don't look vastly different from each other to begin with. And regardless of how thorough such a swap is, if the two characters also trade social roles as a result of the transformation it can become a Literal Transformative Experience as they discover what it's like to be in the other person's shoes.
Often works by way of Liquid Assets. Closely related to Transferred Transformation. The "height swapping" cases are examples of Sizeshifting. If the swapping process involves harming or killing the person with the desired trait, that's Face Stealer. Contrast with Fusion Dance, where two characters become one and merge their physical attributes, and Viral Transformation, where a particular physical trait is passed on without the donor losing it. For the mental equivalent, see Personality Swap (though there's occasional overlap with this trope, especially in stories where The Mind Is a Plaything of the Body).
Examples:
- Brought up jokingly in Azumanga Daioh. When Huge Schoolgirl Sakaki admits that she is still growing and recently went over 170 centimeters, Osaka suggests that she got that tall by "sucking away" the height from Chiyo. This leads Chiyo to start begging Sakaki to "give it back."
- Bakugan: Season 4 introduced the Mutation ability, which lets two or more Bakugan swap physical traits, gaining access to each other’s attacks, along with a large power boost.
- Delicious in Dungeon: Team Touden steps in a circle of changeling mushrooms that makes them all swap races. While they enjoy their new bodies' physical capabilities at first, the party finds the experience insufferable after a while and try to figure out a way to swap back. Notably, the mushrooms can also do things like change a gargoyle into Manneken Pis
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- The premise of Kasane is that Fuchi Kasane can swap faces with other women for twelve hours by kissing them with a magic lipstick. She's a brilliant actress who has a plain face, and she uses the lipstick to impersonate Tanzawa Nina and other fellow actresses who are pretty but have poorer acting skills.
- Living for the Day After Tomorrow: Iokawa Karada is a young girl who lives with her older brother Hiro, while Nogami Shouko is Hiro's ex-girlfriend. Because Hiro left Shouko unexpectedly, she's bitter to the point that she also resents Karada. When they both make wishes at a shrine, they end up swapping ages, with Karada becoming an adult and Shouko becoming a kid. They spend the rest of the series adjusting to the sudden change and trying to understand each other's angst.
- In both the manga and anime (and the readaptation movie Sailor Moon Eternal) for Sailor Moon, PallaPalla casts a spell that causes Usagi and Chibiusa to swap ages, with Usagi becoming younger and Chibiusa becoming older. This briefly prevents them from using their powers, which was PallaPalla's intent.
- The Palaververse: The Tempest: Due to the combined multi-species nature of the Serene Confederation's leaders, Discord adds a bit of a twist to gathering its leaders, by mixing up their body parts, so each of them represent more species instead of just their own. For example:
Emir of Al-Antelus. Except the antelope Emir didn’t have the disproportionately small legs of a warthog. Or the wings of a griffon. Or a certain deficiency of horns.
- In the finale of The City of Lost Children, Miette takes the place of Denrée in Krank's Dream Stealer experiments - only for her to turn the dream against him. As a result, the two of them begin exchanging ages: first, Krank returns to his thirties and Miette grows up into an adult; then Miette reaches middle age and Krank becomes a child, left helpless as Miette dances him around the dream... until at last, Krank shrinks down into a screaming toddler and Miette becomes an ancient crone. For good measure, Krank is then funneled into a nightmare in which he's subjected to the same experiments he forced on so many other children, resulting in him suffering a fatal stroke in the real world.
- Fantastic Four: Rise of the Silver Surfer: As a result of his interaction with the Silver Surfer, Johnny/Human Torch ends up being able to trade superpowers with his teammates. When he does so with Ben/The Thing, he turns into a Rock Monster while Ben returns to his original human form, much to Ben's amusement.
- In The Fly, a Teleporter Accident results in Andre Delambre having his head and arm swapped with that of a fly.
- Plötzlich fett (German for "Suddenly Fat") is a German film about a Formerly Fat personal trainer named Nick who's prejudiced against fat people swapping body weight with an overweight woman named Eva that won a session from him in a raffle. Finding himself suddenly pitied by everyone around him, he slowly falls in love with Eva for being the only support he has left. When everything is restored to normal they become a couple.
- One of the central aspects of Galidor is that the inhabitants of the Outer Dimension have an ability called Glinching that allows them to swap body parts with another person. For example, at one point Euripides the large Frog Man is Strapped to an Operating Table on Earth, so he briefly Glinches with the much shorter Nepol's body below the neck in order to hop out of his restraints. Various characters also swap arms at different points. Part of what makes Nick Bluetooth special as The Chosen One is that he doesn't need to swap with other characters to copy their body parts.
- One episode of Space Cases has the various people on the Christa swapping races with each other after each character complains someone else on the ship has it easier. The swaps also swap most of the character's hair styles as well. In addition it proves that the really happy and really pessimistic ones are that way by genetics.
- The Twilight Zone (1959): In the episode "The Self-Improvement of Salvadore Ross", a man discovers that he can trade his own qualities with those of another person if that person voluntarily agrees to do so. One of his trades is exchanging his youth with a wealthy man's old age in return for one million dollars. He makes a series of trades with other men, paying them $1,000 for trading him a year of their youth in exchange for a year of his old age, and is soon young again.
- Warhammer Fantasy: Van Horstmann's Speculum is a Magic Mirror that switches the user's physical stats (Strength, Toughness, Initiative and Attacks) and the target's during a challenge. However, it always has to be used during a challenge, making it possible to backfire hilariously (it was devised by a Chaos worshipper, after all).
- In Banjo-Kazooie, Gruntilda kidnaps Tooty because she wants to drain the latter's beauty for herself. The Game Over screen shows one specific way this manifests by having Tooty take on Grunty's massive girth.
- Galidor Quest (a browser MMO based on Galidor) lets you choose your species, which determines your head and abdomen, but you're able to trade arms or legs with NPC's you encounter via Glinching, and you're expected to do so in order to meet stat requirements for various tasks. These trades typically have to be won through challenges — but if you lose a challenge and the NPC thinks your limbs are better, they'll take them, which can lead to losing streaks.
- El Goonish Shive: A set of magical scales capable of this appeared in one sketchbook entry. The scales reappeared in a non-canon side story where Sarah and Nanase use them to swap things like height and hip size to be able to fit through small passages, press far-off buttons, and ultimately escape from the room where they found it.
- On DeviantArt, the "attribute swap", "role swap", and "age swap" tags (among others) are used for depictions of characters exchanging physical traits. The most common variations involve two female characters with some connection to each other (usually a mother/daughter duo, but it can also be a teacher/student or boss/employee among other pairings) who magically switch ages and physiques and frequently also decide to trade social roles as well.
- Breadwinners: When SwaySway and Buhdeuce eat a loaf of Switcheroo Bread, they switch physical builds (SwaySway becomes short, Buhdeuce becomes tall), powers, and traits (SwaySway now has Buhdeuce's Big Eater tendencies).
- CatDog: In the episode "Smarter Than the Average Dog", Cat tries to make his conjoined twin brother Dog smarter by showing him educational VHS tapes. Dog does become much smarter and gets a massively enlarged brain after watching the videos — but he somehow drained the neurological matter from Cat, who's cranium has visibly shrunken and left him much dumber as a result. Cat rapidly watches the videos himself, giving himself the huge brain and leaving Dog even dumber than he was before. The two do this video watching back and forth and even physically shove the brain matter from one head to the other in a frantic bid to be the smart brother until they're ultimately left with the same brain sizes and intelligences they had at the start.
- The Fairly OddParents!: "Blondas Have More Fun!" has Wanda and her identical sister exchanging lives for the day, which is easily done by simply switching their hair colors. Blonda-as-Wanda can't believe what it's like to put up with Timmy and Cosmo's reckless stupidity and having Jorgen blame everything on her, while Wanda-as-Blonda nearly accidentally destroys the former's acting career.
- In Gargoyles, a magical contract between Macbeth and Demona transfers his youth to her, then freezes them at those ages.
- In the George Shrinks episode "George Un-Shrinks", the three-inch-tall ten-year-old and his normally-sized father Harold switch sizes. George becomes a normal-sized kid and Mr. Shrinks becomes three inches tall, and the conflict of the episode comes from both George and his dad having to get used to their new sizes in order to keep house while Mrs. Shrinks is away, something that's made even more complicated when toddler Junior Shrinks also suddenly becomes the size of a small elephant. In the end, it turns out that it was All Just a Dream George, Harold, and Junior had while watching B-movies on TV (though all three vividly remember the events of the episode happening).
- In one episode of The Grim Adventures of Billy & Mandy, Grim and Billy decide to switch places for a day, with Grim going to school and Billy filling the role of The Grim Reaper. Initially, they only swap wardrobes, but eventually they start changing physically as well, with Grim becoming a fleshy, bulbous-nosed human and Billy becoming a skeleton.
- The Ren & Stimpy Show: The episode "Who's Stupid Now?", pictured above, has the eponymous duo going through a Personality Swap that, as a side effect, causes them to trade physiques as well. So the Lean and Mean Ren and the Fat Idiot Stimpy become Fat Idiot Ren and Lean and Mean Stimpy.
- Sesame Street: This was the basis for a series of animated inserts by Cliff Roberts in the early 1970s, in which two dissimilar animals, such as an elephant and a mouse, switched bodily features.
- In one episode of Totally Spies!, the Villain of the Week runs an agency that kidnaps supermodels and uses a contraption which switches their body parts with those of other women. A freckled, redheaded character with braces and stocky legs and hips gets Clover's legs, Alex's bob cut, and Sam's unfreckled skin and smile.
