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[[quoteright:350:[[Series/TheTwilightZone1959 http://static.tvtropes.org/pmwiki/pub/images/twilight_zone_the_masks_2718.jpg]]]]
[[caption-width-right:350:L - R: [[RichBitch Emily]], [[CorruptCorporateExecutive Wilfred]], [[JerkJock Wilfred Jr.]], and [[{{Narcissist}} Paula]] after receiving some [[KarmicTwistEnding karmic justice]].]]
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-> '''Witch:''' Taint of mutant, scum of pond, thou shall become the guise thou donned!\\
'''Carl:''' ''[confused]'' Speak English, moron!\\
'''Witch:''' ''[exasperated]'' I'm ''turning you into your costumes.''\\
'''Homer:''' Well, are ya gonna talk about it or are you gonna do it? ''[zapped]''
-->-- ''WesternAnimation/TheSimpsons''

It's AllHallowsEve (usually) and the kids are trick-or-treating and everything is normal, but something magical is afoot, and turns people into whatever costume they are wearing. If you're dressed up as a werewolf, for example, you'll ''become an [[OurWerewolvesAreDifferent actual werewolf]]''.

You'd be surprised just how often this happens in fiction.

Not to be confused with BecomingTheMask or EvilCostumeSwitch. Can overlap with TheMindIsAPlaythingOfTheBody, which is [[OhCrap bad news]]. Related to EvilMask. [[HilarityEnsues Hilarity might ensue]] if overlapped with ForHalloweenIAmGoingAsMyself.

May be the subject of a HalloweenEpisode.



[[folder:Anime & Manga]]
* In ''Manga/{{Berserk}}'', the leader of a cult dressed in a goat's head and used a snake as a fake penis. He gets transformed into an Apostle Spawn, which turns him into a real goat-headed, satyr-like monster with a snake for a penis. [[spoiler: Before his transformation he was about to perform a sexual ritual with Casca, who was believed to be a goddess by the cult. After transformation the only thing he can think of is raping her. Luckily for her, he runs into Guts.]]

[[folder:Comic Books]]
* At least one character in ''ComicBook/ThereforeRepent'' transforms thus.
* Happens at a [[AttackOfTheTownFestival revived pagan festival]] in ''ComicBook/{{Hellblazer}}'', to the detriment of everybody. [[spoiler:(New father in baby costume to infant: "You're taking all of mummy's attention and it's! not! fair!" *splat*; a dentist(?) with a rictus grin mask wants [[StepfordSmiler EVERYONE]] [[GlasgowGrin TO]] [[SlasherSmile SMILE!]]). This isn't transformation, but rather a crazy-making signal coming from the nearby underground nuclear base. John and his friend discover that [[ThePowerOfRock loud punk rock]] cancels the effect a little too late: an ex-fighter pilot is "cured" just seconds after he releases a bomb, destroying the town and everyone in it (except John, of course).]]
* This is part of the premise and played for laughs in the indy comic ''ComicBook/TheUnderburbs''. The main character, Angie and [[spoiler:her mother]] turn into a witch and her brother into a monster. None of this effects life in the town very much.
* ''ComicBook/DoctorWhoMagazine'' has one issue where the backstory involves all the nobles of a planet being turned into the animals that they dressed up as in celebration of surviving a plague that killed ten thousand peasants.

[[folder:Fan Works]]
* The focus of the [[FandomSpecificPlot Yet Another Halloween Fic a.k.a. YAHF]] in ''Series/BuffyTheVampireSlayer'' fanfiction.
* Like ''Buffy'' fans before them, the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' community made this popular as a way to make their characters into powerful villains, or, less commonly, heroes.
* ''Costumes'', a fic in ''Fanfic/RainbowDoubleDashsLunaverse'' revolves around this trope. In an attempt to promote her wares, Rarity uses a Zebrican ritual which she thinks will make her costumes more realistic. Unfortunately, in something of a RunningGag for the Lunaverse, she's misunderstood the function of the ritual. The ritual actually was designed to allow a Zebra to take on the physical form and powers of a totem. So everyone wearing one of Rarity's costumes (and most of Ponyville was wearing one of Rarity's costumes), was transmuted into whatever they were dressed up as, and gained whatever abilities they subconsciously believed their new form should have. So Rarity, for example, was turned into a vampony and gained hypnotic eyes and blood-sucking fangs. To make matters worse, the spell also caused all the victims to believe that they actually were whatever they'd been dressed as. Luckily, Trixie and Twilight had made their own costumes, and were able to dispel the curse. But not before several adventures had occurred...
** Snips and Snails had dressed up as Captain Equestria and Spiderstallion respectively, while Raindrops was in disguise as Princess Platinum. When Raindrops!Platinum was kidnapped by a pack of Diamond Dogs (formerly the workers of Sweet Apple Acres), the two superheroes rescued her. Snips!Captain even got a kiss out of it... right as the magic was dispelled, so Raindrops ended up kissing Snips.
** Cherilee, dressed up as and turned into Catmare, attempted to rob a jewelry store before running afoul of Batstallion (formerly Heavy Roller) and Robin (formerly Scootaloo). After an innuendo-laden fight, they successfully catch her, only for Carrot Top to show up transmuted into Poison Ivy. Carrot!Ivy takes Batstallion prisoner with her spores, expressing an interest in feeding him to her plants. Cherilee!Catmare can't have that, as she has her own designs on Batstallion's body. The ritual comes undone right in the middle of the final fight between Catmare and Robin on one side, and Poison Ivy on the other.
** Lyra and Bonbon had dressed up as [[Film/BonnieAndClyde Bonnie and Clydesdale]]. And in that guise, they successfully robbed the Ponyville bank, leaving the teller tied up behind them. They had just finished enjoying some celebratory sex when Dinky!Holmes and Ditzy!Watson show up and incapacitate them. Dinky!Holmes then rounds things off by apprehending the teller, who'd been embezzling from the bank. That chapter ends with Bonbon worriedly rubbing her abdomen after the magic is reversed.
* Website/{{Fenspace}}: This is a possible result of handwavium accidents. The most drastic example to date is [[http://www.fenspace.net/index.php5?title=Wave_Convoy a guy]] who built a Trasformer using handwavium and got shot by a police sniper after being mistaken for a terrorist. He passed out in the cab, with a burst pipe leaking handwavium into the wound, and woke up with his mind now in the Transformer body. Likewise, [[http://www.fenspace.net/index.php5?title=Shuko the first catgirl]] was created when a con-goer in a handwavium-enhanced catgirl costume ate food contaminated with Guacamole (a strain of 'wavium specialized for bio-modification), and [[http://www.fenspace.net/index.php5?title=Jet_Jaguar another guy]] became a cyborg when he [[AlcoholInducedIdiocy accidentally]] drank a bottle of handwavium while wearing a suit of PoweredArmor.
* ''Fanfic/OversaturatedWorld'': In "[[https://www.fimfiction.net/story/323071/74/group-precipitation/living-nightmares-by-jenna-cipher Living Nightmares]]", Twilight performs an experimental costume-related spell that results in the creation of Darth Rarity, Sweetie Skywalker, Chief Engineer Applebloom 'Scotty' Scot, Invader Spike, and Rainbow Caboose.
-->'''Sunset:''' "What have we learned, Twilight?"\\
'''Twilight:''' "Don't take magical inspiration from ''[[Series/BuffyTheVampireSlayer Peppy the Vampire Stabber]]''?"\\
'''Sunset:''' "I meant test new spells in a controlled environment, but that's probably a good rule of thumb as well."

[[folder:Films -- Animated]]
* This appears to be the premise of the upcoming film Monster Family.

[[folder:Films -- Live-Action]]
* The Creator/DisneyChannel Original Movie ''Film/{{Halloweentown}} II'' had this, with the villain planning on turning every human who dressed as a monster into that monster (and conversely turning monsters into humans). He even had the heroine's mother wear a horrific mask so that she would become a terrifying monster.
* This happens in the 2003 movie ''Hallow's End'', in which the characters become their costumes when they die.
* In ''Film/NightOfTheDemons3'', the demonic Angela Franklin turns characters into their demon, CatGirl, and snake-armed gorgon costumes.
* ''Film/TheSorcerersApprentice'' has TheDragon Horvath turning a Chinese dancing dragon into a real dragon.

* The ''Literature/{{Goosebumps}}'' book ''The Haunted Mask'' (also adapted for TV) had this.
* Literature/FlossieTeacakes's magical coat may be a benign version of this -- a particularly fabulous coat that she finds in her older sister's room turns out to magically transform dowdy ten-year old Flossie (when she plays at dressing as her sister) into [[OlderAlterEgo the young woman that she dreams of being]].
* In one of the Franchise/DoctorWhoExpandedUniverse books, ''Forever Autumn'', this happens because of some strange occult-sciency aliens wanting to harvest fear from everyone so they can leave Earth. Yes, ClarkesThirdLaw is in effect here.
* ''TabletopGame/MagicTheGathering'': In the ''Literature/{{Ravnica|Cycle}}'' tie-in novel, Agrus Kos and his angel partner, Feather, arrest a troupe of actors after a faulty "Performance Enchantment" causes the man playing a bloodthirsty Gruul war chieftain to get a little too in-character. Fortunately, nobody is injured.
* In Creator/{{Robert Bloch}}'s "The Cloak" the title garment gave the guy who was wearing it vampiric urges.
* There's a brief bit during Geoph Essex's ''Jackrabbit Messiah'' where the hero (and his HelpfulHallucination) have to JourneyToTheCenterOfTheMind. While there, Jack's [[IconicOutfit costume]] is no longer ''just'' a costume!

[[folder:Live-Action TV]]
* ''Series/BuffyTheVampireSlayer'':
** Season 2, Episode 6: "Halloween". This episode is one of the fandom's [[FandomSpecificPlot favorite launch points]] for crossover {{Fan Fic}}s in which someone dressed as a character from another fandom, to the point where "YAHF" (Yet Another Halloween Fic) has entered the fandom vocabulary.
** Exploited in the Season 4 episode "Fear Itself" when the gang attend a college Halloween party and all dress up as someone or something that would actually be useful should history repeat itself.
* The same trick was pulled on a convention in the later Series/{{Angel}} comics, turning a bunch of nerds into superheroes and villains, and turning Spike into Angel. Or at least, [[HilarityEnsues Angel as Spike sees him]].
* ''Series/TheTwilightZone1959'' has "[[Recap/TheTwilightZoneS5E145TheMasks The Masks]]", where a dying millionaire forces his worthless heirs to wear masks caricaturing their worst personality traits - if they take them off before midnight, they get cut out of his will save for some fare to take the train home. At midnight, he dies, and they shed the masks... and discover their faces have taken on the shapes of the masks permanently save the good-hearted millionaire. He retains his human face. It should be noted this isn't set on Halloween, but Mardi Gras in New Orleans.
* Abed from ''Series/{{Community}}'' is probably worth an honorable mention. In the Halloween episode "[[Recap/CommunityS1E07IntroductionToStatistics Introduction to Statistics]]", he dresses up as Batman, and although technically he never actually turns into Batman (despite appearances, it's not that kind of show), he commits to the part to such a degree that some of his friends start to think he actually believes it. But then, he ''is'' known for his [[AmbiguousDisorder rather]] [[CloudCuckooLander unique]] [[MetaGuy view]] of reality.
* ''Series/{{Misfits}}'' has an unusual example bordering on an inversion: One character wears a gorilla costume to a costume party. In the end it turns out that he was a gorilla with the superpower to appear human, leading to a scene in which he removes a gorilla mask to reveal a gorilla face underneath.
* In one episode of ''Series/SirArthurConanDoylesTheLostWorld'', the heroes take shelter from the rain in a castle. When they decide to change out of their wet clothes into the formal outfits they find, they become possessed by the original wearers, who were evil. Fortunately, Challenger didn't do this, leaving him free to save the day.
* In one episode of ''Series/MyBabysittersAVampire'', one of the characters, Rory, puts on an ancient magical mask that gives him the power to turn people into their costumes. Unfortunately, the mask also takes control of his mind, and starts building an army. To make matters worse, the mask can only be removed after the wearer is blasted with magical lightning- something WAY out of the league of the resident wizard, especially since his OldMaster witch grandmother is out of town.
* The Halloween costume version is also used in ''Series/{{Spooksville}}'', featuring a boy who keeps trick-or-treaters hostage as more-or-less real versions of their costumes. The resolution hinges on one of the characters being able to use part of his costume that had been a toy but was now real.

[[folder:Tabletop Games]]
* In ''[[TabletopGame/MonteCooksWorldOfDarkness Monte Cook's World of Darkness]]'', all of the costumes at the Guthrie Theater in Minneapolis work this way. Once someone puts on a costume, they become that character--even when the costume is removed. The effect is apparently irreversible. The theater is popular with suicidal people; by putting on a costume, they can cease to exist and instead become someone else entirely.

[[folder:Video Games]]
* The Deku, Goron, Zora, and Fierce Deity masks in ''[[VideoGame/TheLegendOfZeldaMajorasMask Majora's Mask]]'' are much more than facial accessories...
* This is a gameplay mechanic in the Creator/DoubleFine RPG ''VideoGame/CostumeQuest''. You play a kid who has to rescue their sibling from evil goblins using powers channeled through their costume.
* ''VideoGame/KidChameleon'' on the Sega Genesis as the main gameplay mechanic. The eponymous Kid Chameleon gains different powers and costumes from various mask power-ups found throughout the game.
* Played with in a skit in the [=PS3=] version of ''VideoGame/TalesOfVesperia'', where the party unintentionally start acting like the Tales characters they're dressed as. The same costumes also let them use an arte that was used by the character it belonged to.
** This is also the primary gameplay mechanic of the ''Narikiri Dungeon'' series, where donning the costumes of different classes, monsters, or Tales characters turns you into them and allows the use of the appropriate abilities.
* In ''VideoGame/SunlessSea'', there is an island called Visage where all who visit the island must don a mask to go past the dock onto the island. Those who wear the mask take on the role of the mask, both mentally and physically. For example, those wearing the frog mask will only croak when they try to speak, someone wearing a locust mask will act like a locust, and while wearing the mask of the moon-moth it's mentioned "You briefly flicker your wings". However, once someone removes their mask they immediately become the person they were before.
* Tales played with it before in ''VideoGame/TalesOfTheAbyss'', where Anise can be given special dolls from other Tales or Namco games (such as Presea from ''VideoGame/TalesOfSymphonia'' and ) which sometimes prompt Anise's end battle quote to sound ''nothing like'' anything Anise would say and sometimes end up as nonsequitors, because she's channelling the character in question. They also allow her to use their special abilities (ie, Beast for the Presea doll)
* ''VideoGame/FiveNightsAtFreddys3'': Purple Guy's [[spoiler:ultimate fate, where it is revealed he suffered a grievous, painful death and became entombed in the very same suit he used to commit his crimes, his restless ghost haunting it to this day.]]
* Most legendary skins in ''VideoGame/{{Overwatch}}'' give the characters additional lines and/or change existing ones to fit the skin's theme.
** Hanzo's Lone Wolf and Okami[[note]]Japanese for "wolf"[[/note]] skins are very good examples, as they not only replace all dragon-related lines with wolf-related ones (i.e. "See through the dragon's eyes" is changed to "See through the wolf's eyes"), but they also change the dragons that spawn from his Ultimate into wolves, complete with a chorus of howls.
** Another good example is Zenyatta's Cultist skin from the 2017 Halloween event, which turns him into a mechanical {{Cthulhumanoid}}. His voice lines are normally very tranquil and reflect his insightful and {{religious|Robot}} nature, but with this skin become darker, more menacing, and bring eldritch themes to mind -- "the Iris embraces you" becomes "the Iris consumes you", "experience tranquility" becomes "experience... nothingness". Also, the three pairs of holographic arms that appear during his ultimate ability are replaced by three pairs of jointed mechanical tentacles.
** Symmetra's [[DraconicHumanoid Dragon]] skin, also from the Halloween event, visually makes her resemble a half-draconic [[EvilSorcerer sorceress]], changing her weaponry to gain more fantasy-style armor plating and [[EyesDoNotBelongThere moving, reptilian-looking eyes]]. She gains some appropriately demonic and fiery lines, and all her ability lines have been changed to [[DoingInTheScientist do in the scientist]], now referring to her Sentry Turrets as "Sentry Wards," her Teleporter as a "Teleportation Portal," and her Shield Generator as a "Shield Well."

[[folder:Web Original]]
* The ''Literature/XanaduStoryverse'' is all about this. At [[http://shifti.org/wiki/Xanadu_(setting) a costume convention]] with ten thousand in attendance, costumes become real and those wearing them are changed. Mentally the transformation varies from person to person, from "Suddenly my costume is much more accurate" to "Where am I, what is this planet?", due to each costumed person technically being turned into what they perceived their costume as being -- as such, two people in the same exact costume would still turn into different things based on their knowledge and interpretation of the character they had come as, how "in-character" they were, what they were thinking or doing at the moment they transformed, and so on. There is also the "clothing curse", which affected some, but not all, of the transformed people and caused any clothing they put on to transform in the closest equivalent that would be "appropriate" for their character to wear[[note]]so for instance anything a Jedi would put would transform into a set of robes[[/note]]. Stories tend to be either UsefulNotes/{{furry|Fandom}} or WelcomeToTheRealWorld.
* Overlaps with DraggedIntoDrag on sites like Big closet top shelf all the time.
* [[WesternAnimation/MyLittlePonyFriendshipIsMagic Discord]] inflicted this upon ''Roleplay/InkCity'' when he crashed their Halloween party. This included several residents temporarily transforming into ''each other'' thanks to their costume choices, like [[WesternAnimation/RegularShow Rigby]] becoming [[WesternAnimation/AeonFlux Trevor]], and [[WesternAnimation/{{Animaniacs}} Yakko]] becoming his own player.
* In general, this is a favorite [[HalloweenEpisode Halloween event]] for JournalRoleplay games.
* From the satirical Venezuelan blog ''[[Blog/ElChiguireBipolar Chigüire Bipolar]]'''s article [[http://www.elchiguirebipolar.net/03-03-2014/nino-se-disfraza-de-gnb-y-le-pega-a-su-mama-abuela-y-perrito/ *Boy disguises as National Bolivarian Guard and hits his mother, grandmother and doggy]], both the title's boy and his sister who disguised as radical oppositor.
* ''Website/TLFTravelAlerts'': For [[https://twitter.com/TlfTravelAlerts/status/395954722450210816 Halloween 2017]] they warned of a student who dressed as a circle line train in 1997 who became an example of this trope and was still running in service. Consider your costumes wisely!

[[folder:Western Animation]]
* In ''WesternAnimation/TheFairlyOddParents'' Timmy wishes for this to happen on Halloween -- unfortunately for him, his wording of the wish prevents him from unwishing it. He wanted everyone's costumes to be "real and scary"... and his fairy god parents just had to dress as a "floating human janitor" and a "floating human nurse". Even worse, the popular kids were dressed as Crash Nebula villains capable of forming a doomsday device that can blow up a planet.
* ''WesternAnimation/TheSimpsons'':
** In the third segment of "[[Recap/TheSimpsonsS17E4TreehouseOfHorrorXVI Treehouse of Horror XVI]]", "I've Grown a Costume on Your Face," a witch curses everyone in town by making them become their costumes.
** One of the Halloween ''comics'' had this happen in messy fashion when Rod and Todd Flanders became possessed by demons, including a lethal HowDoIShotWeb when Comic Book Guy, dressed as Franchise/{{Superman}}, tries to test out his X-ray vision on stuff in his pocket and sets his eyes to heat vision instead.
* In the ''WesternAnimation/DarkwingDuck'' episode "Slaves to Fashion", Tuskernini, the villainous walrus filmmaker, creates a gas that causes people to take on the personality of whatever costumed character they dressed up as. HilarityEnsues. The gas doesn't actually affect our hero, though, because [[ForHalloweenIAmGoingAsMyself he came to the party as himself.]]
* The "Curse of Necklace" episode of ''WesternAnimation/MartinMystery''.
* Happened in the ''WesternAnimation/DannyPhantom'' special, "Reality Trip" where a Reality Gem transformed a trio of nerds at a comic convention. Unfortunately for Danny, they were dressed as super villains.
* The ''WesternAnimation/CreepSchool'' episode "Tricks That Treat" does this.
* In the ''WesternAnimation/{{Rugrats}}'' episode, "Curse of the Werewuff", Angelica convinces the babies that they will be transformed into their Halloween costumes.
* The TV special ''Witch's Night Out'' (1978) has a witch turn two kids and their babysitter into the monsters they're costumed as. When the adults find out and turn on her, she explains that the point of Halloween is to try out different personas and imagine your potential. The adults happily start calling out requests for one-night transformations themselves.
* ''WesternAnimation/BatmanTheBraveAndTheBold'' has Franchise/{{Batman}} turn into a man-bat hybrid, Bronze Tiger into a tiger-human hybrid and Vulture, Fox and Shark turn into, you guessed it, subjects of {{Animorphism}}.
* Without the Halloween aspect, this was the premise of the 1980s children's animation ''MrBenn''. Mr. Benn (a bowler-hatted Everyman) would visit a magical costume shop, try on a costume and become that character -- spaceman, cowboy, prisoner, clown...
* There is an episode of a BBC Schools programme called ''WesternAnimation/TheMagicKey'' which plays this trope to a T. The children are about to go to a fancy dress party when, like in every episode, they are sucked into a magical world via the Magic Key. In this one they meet a farmer whose crops are being eaten by a group of rooks, led by an anthropomorphic leader called the Rook King. When the children try to help the farmer, the Rook King turns them all into their costumes using his staff and they have to work out a plan to defeat him whilst trapped in their new forms. Once they capture him and get hold of the staff, they turn back to normal.