Something's starting to happen to one of our characters - [[VirusVictimSymptoms maybe he's been infected with some virus]]... [[MadnessMakeover Maybe he's going crazy]]... [[Webcomic/CyanideAndHappiness Maybe he's just gaining weight]]. Whatever it is, it's usually not directly explained, and we don't see him changing on-screen...

It's just that one day, he looks a little bit... off.

And each time we see him after that, the change is a little more noticeable, usually until it reaches either [[RefugeInAudacity hilarious]] or [[BodyHorror horrific]] levels.

As mentioned above, this is nearly always either PlayedForLaughs, or PlayedForDrama as TransformationHorror.

A SuperTrope to VirusVictimSymptoms, EvilMakeover, and MadnessMakeover and a SisterTrope of TransformationAtTheSpeedOfPlot. Contrast ObliviousTransformation, where a character isn't even aware of the charges to their body.

May also overlap with {{Metamorphosis}}, which is often a gradual process.

AndThenJohnWasAZombie is sometimes the end result.

See FisherKingdom (more specifically the second variant) for when simply being in a certain place can have this effect.



[[folder: Anime & Manga]]
* In ''Anime/TheCatReturns'', the protagonist becomes more [[CatGirl catlike]] the longer she remains TrappedInAnotherWorld.
* In ''Anime/{{Simoun}}'' everyone is born female and upon turning seventeen go to a mystical spring where they choose to either remain female or become male. For those who choose to become male the process is a SlowTransformation. For example head mechanic Wapōrif went to the spring and became male two years before the series but still has the biggest bust in the series.
* Happens to the snail people in ''{{Manga/Uzumaki}}'', who develop a spiral pattern on their backs, then start developing other, more horrific traits over the course of several days.
** In general, this seems to be a favorite trope for {{Creator/Junji Ito}}. Possibly the most horrific example occurs in a six page short titled "Hell O'Dollies", in which a child contracts [[TheVirus Early Onset Doll's Disease]]. She transforms first into something like a living doll, then into something that hopefully hasn't been a living ''anything'' for a long time.
* In ''{{Manga/Naruto}}'', the process of turning humans trapped in the Infinite Tsukuyomi into White Zetsu takes several years.

[[folder:Comic Books]]
* In ''ComicBook/TeenTitans'' when Raven was being influenced by her father's power it effected her appearance slowly giving her more gaunt angular features and a [[ForeheadOfDoom taller forehead]] until she fell under his sway and turned on the team. ([[RecycledScript The first time it happened]].)

[[folder: Fan Works]]
* ''Fanfic/{{Pokeumans}}'': The transformation into a Pokeuman takes a whole week. [[{{Metamorphosis}} And is irreversible]].
* The ProjectDarkJade fanfic ''Fanfic/{{Webwork}}'' has Jade change into a [[spoiler: Jorōgumo]] over the course of 8 years.
* ''Fanfic/TheGolds'': It is casually mentioned that nonhuman curse-victims and magical creatures in Storybrooke like Katja and Ruby started exhibiting their pre-Storybrooke traits slowly after the curse was broken.

[[folder: Film]]
* The protagonist of ''Film/TheSantaClause'' slowly changes to fit the part of Santa (gaining weight, becoming unable to shave).
* The werewolves of the ''Film/GingerSnaps'' films transform slowly into wolflike creatures, over the course of days or weeks.
* Seth's horrific transformation in ''Film/TheFly1986'' starts out gradually with his fingernails becoming loose and his face having a subtle discoloration to it. Then his body parts begin falling off, starting with his ears, and the BodyHorror climaxes with his decaying human skin being torn apart to reveal his true mutant fly form.
* [[spoiler:Wikus]]'s transformation into a Prawn in ''Film/{{District 9}}'', to the point where by the very end, [[spoiler:he's become one entirely.]]
* In ''Film/LostInSpace'' Dr Smith receives a spider bite -- two decades later [[spoiler:he's transformed into a huge spider creature]].
* ''Film/{{Honeymoon}}'': Bea's strange behavior and physical degradation over the course of her honeymoon is the result of [[spoiler:being taken over by an alien puppeteer parasite. It gains more and more control over her mind and slowly transforms her into a host body. She's aware of the process the whole time and is unable to do anything about it]].

[[folder: Literature]]
* People turning into donkeys in ''Literature/TheAdventuresOfPinocchio''. In the original story, it took several days for the first part of the change (the ears) to occur.
* In Creator/HPLovecraft's ''Literature/TheShadowOverInnsmouth'', the inhabitants of Innsmouth are born as humans, but slowly turn into fishmen over the course of their lives.
* When Tash is infected in ''Literature/GalaxyOfFear'' she starts off with a rash that, through that story, swells and spreads, sends off TaintedVeins, and she sweats and is unusually irritable. Then the rash starts oozing... then the ooze proves to be [[spoiler: tendrils of the BlobMonster that she's [[TheVirus turning into]]]] and moving about as the transformation speeds up. This is in a day or so.
* Stock in trade of the [[EvilutionaryBiologist Evilutionary Biologists]] in ''Literature/TheMoreauFactor''. Somewhat mitigated by the fact that their victims are mostly other scientists deliberately chosen because they would find the research opportunities presented by their transformations (if not the actual transformations themselves) intriguing.
* In ''Literature/{{Seraphina}}'' Dragon's muscles are soft, and their wings incapable of flight for the first few minutes after transformation.
* In ''Literature/LordOfTheRings'', Gollum's transformation from hobbit to.... ''thing'' was centuries-long. It is implied that the Nazgul's transformation from humans to dark holes in reality was one, too.
* In ''Literature/WarriorWolfWomenOfTheWasteland'', having sex causes the women of [=McDonaldland=] to start transforming into wolves. This happens anytime they have sex, and it is irreversible.
* ''Literature/{{Dracula}}''. Due to Dracula nightly visits to feed on Lucy, she becomes weaker over time and observes that her senses have suddenly become keener but she continues to have nightmares of dark beings. By the third visit, she's lost so much of her blood that her bite wounds eventually close up on their own, she gains fangs and her demeanor is uncharacteristically more seductive, signifying to Helsing it's too late to save her from becoming a vampire. Mina's transformation is slightly different due to Dracula feeding her his blood, cursing her to turn regardless if she stays alive or dies as long as he's alive. Indeed, she starts showing signs due to losing appetite for food, her canines slowly turning into fangs, sharing a psychic connection to Dracula and being unable to stay awake during the day but being much more lively at night.
* Though most of it happens off-screen, Francis Leicester [[ArthurMachen Arthur Machen's]] ''Novel of the White Powder'' undergoes one of these after he starts taking regular doses of the titular powder in the belief that it's his prescribed antidepressant. It starts with his appearance provoking a vague UncannyValley response in his sister, Helen. It ends with a [[ImMelting formless puddle of black protoplasmic ooze, seeping through the floor of his bedroom and into the room below]], [[AndIMustScream and yet still very much alive]].

[[folder: Live-Action TV]]
* ''Series/TheOuterLimits1995'': In the episode "Birthright", a U.S. Senator escapes from his security detail after his own men try to kill him, and gradually gets weird warts and such. It turns out that a race of [[TheReptilians reptiloid aliens]] had sent spies to study humans and the spies are turning back after the disguise wears off. The horror factor is the spies themselves didn't know they were aliens.
* God!Castiel in ''Series/{{Supernatural}}''
* The ''Series/RoundTheTwist'' episode "Nails" starts with a distressed boy showing the protagonist he now has three rows of nails, and telling her he's turning into a monster. By the end of the episode, he has become [[spoiler:a merman]].
* The Halloween episode of ''Series/{{Thats So Raven}}'' has Raven and Chelsea slowly turning into cows over the course of the episode. While their physique is human, they get cow ears, tails, snouts, hooves, tongues, and also start eating and mooing like them. At the end of the episode [[spoiler: they are completely transformed, but it is revealed that it was actually one of Raven's visions that she manages to prevent from happening]].

[[folder: New Media]]
* [[ Ted Bear's weight gain]] in the ''Webcomic/CyanideAndHappiness'' short.
* Michael Swaim's... Um... "Cuteification" in ''[[ Vids They Thought Would be Cute.]]''
* Our own page description for SugarBowl.

[[folder: Tabletop RPG]]
* ''TabletopGame/DungeonsAndDragons'' has "artifact transformation" -- some artifacts gradually transform their users into "the proper owner" image -- physically, mentally or both.
** [=WG5=] ''Mordenkainen's Fantastic Adventure''. The Kaftan of Ogrishness slowly turns its wearer into an ogre over a period of three days.
** D3 ''Vault of the Drow''. Anyone possessing the idol of Lolth will, over 66 days, slowly turn into a giant spider.
* ''TabletopGame/CallOfCthulhu''. As [[HalfHumanHybrids Deep One hybrids]] are growing up they appear to be human. When they reach the appropriate age, they slowly change into Deep Ones and go off to join their fellows.
* ''TabletopGame/{{GURPS}}''
** ''Space Adventures'', adventure "Rebirth". A genetic virus called Proteus can slowly change a human being into an alien.
** ''Fantasy Folk''. A Fishmen artifact can slowly change its user into a Fishman.
* ''Dark Conspiracy''. The ''Darktek'' supplement had Empathic Viral Mutators, a virus that could change the victim into another creature over a period of 48 hours.

[[folder: Theatre]]
* Played for drama in the [[AllMusicalsAreAdaptations stage adaption]] of ''Theatre/BeautyAndTheBeast''. Instead of being [[KarmicTransformation transformed instantly]] like in the [[Disney/BeautyAndTheBeast Disney movie]], the inhabitants of the castle slowly change into objects, until they can no longer move, speak or even see.

[[folder: Toys]]
* In ''Toys/{{Bionicle}}'', after the Piraka bathe in mutagenic water for a short while, thanks to falling into a trap, they don't notice it, but they start developing aquatic capabilities. When we next meet them a couple of books later, we find that their whole bodies have diminished, reducing them to eel-like spines with their heads at the end.

[[folder: Video Games]]
* In ''VideoGame/GuildWars Nightfall'', Varesh transforms into a Margonite like appearence (and eventually a full margonite form) over the course of several missions. This involves getting 2 extra pairs of eyes (first appearing as bumbs, then fully appearing) and become a lot paler.
* The Wanderer over several cutscenes in ''VideoGame/{{Diablo}} 2'' gradually looks more and more evil, until in a final cutscene morphing fully into a Diablo form.
* In ''VideoGame/EternalDarkness'' one of the characters you play as is inflicted with a curse in their chapter, meaning he gradually rots and turns into an undead creature (this happens at set points in the level) while he tries to to warn Charlemagne before he meets the same fate. [[spoiler: He fails and ends up trapped in a room in the church as an undead monster until another character finally puts him out of his misery in a boss battle [[AndIMustScream a few hundred years later]].]]
* ''VideoGame/TheHauntedRuins'': The general shopkeeper slowly transforms from a seemingly innocent girl into [[spoiler:an evil witch]] the deeper you venture into the dungeon. At first it looks like she just put on makeup, [[spoiler:but then she gets PointyEars, her cashier uniform becomes a skimpy dress, and a tiara and pointy nose begin to gradually form on her. This transformation is mostly amusing to watch because of how she keeps on insisting that her changing appearance is all in your head and how you simply MUST show the fabled "[[ArtifactOfDoom Dark Orb]]" to her as soon as you find it, mmkay?]]
* The protagonist of ''VideoGame/ShadowOfTheColossus'' gradually becomes battle-worn as he kills the Colossi. [[spoiler:There is, eventually, an explanation for this.]]
* The monsters and face blocks from ''VideoGame/{{Eversion}}'' undergo this as you gradually evert from [[SugarBowl World X-1]] to [[{{Mordor}} World X-8]].
* In ''VideoGame/{{Skullgirls}}'', this happens to [[spoiler:Filia]] during her ending: Upon finding the [[JackassGenie Skull Heart]], she wishes for [[spoiler:Painwheel to return to normal]], a seemingly pure wish that should be granted without problem by the Skull Heart [[note]]If the Skull Heart decides your wish is impure, you become the next Skullgirl[[/note]]. However, the Skull Heart finds that her motivations are not entirely selfless: [[spoiler:Filia's wish is partially motivated by her desire to atone for her actions during her life as a member of [[TheMafia Medici family]]]]. As a result, poor [[spoiler:Filia]] is next in line for the title of Skullgirl, but since the wish was not entirely selfish, the transformation is not instant, allowing her to at least enjoy life with [[spoiler:her childhood friend]] for a while.
** A similar thing happens in [[spoiler:Parasoul]]'s ending. In order to [[spoiler:save her sister, Umbrella, from becoming the next Skullgirl]], she wishes that [[spoiler:Umbrella will never become the Skullgirl]]. The Skull Heart grants the wish by [[spoiler:Making Parasoul take her place]]. The transformation is slow enough for her to [[spoiler:train Umbrella to defeat her when she finally turns]].

[[folder: Web Comics]]
* In ''Webcomic/{{Exiern}}'' Dragons are born looking like humans and gradually transform into their true forms after they mature. The protagonist's sidekick/like interest (she can't admit to more than that) Denver is a larval dragon, though he doesn't know it. His sister was well along in her transformation when she was last seen.
* In ''Webcomic/{{Goblins}}'' Complains is affected by a magical power that tries to [[ turn him into a demon]]. It's quickly dispelled, but every time he's badly injured, [[ he heals]] with more demonic features: AlienBlood, a [[RedRightHand demon arm]], GlowingEyesOfDoom, and so on.
* ''Webcomic/DraculaRulerOfTheNight'': As in the novel, Lucy goes through gaining fangs and having sharper senses. But here Helsing notices her ears are likewise becoming more misshapen to add to the symptoms. By the time she turns, they're completely pointed. When Mina is bitten, she likewise gains this as an added symptom as well as her normally short hair starting to grow out down her shoulders as a surprisingly increasing rate.

[[folder: Web Original]]
* In ''WebVideo/TheCartoonMan'', Roy's initial transformation into a human cartoon character takes several days.
* ''Literature/WhateleyUniverse'': Some transformations from the Exemplar power have been said to take at least a year to fully complete.

[[folder: Western Animation]]
* The Alchemist's transformation into Skeleton King from ''WesternAnimation/SuperRobotMonkeyTeamHyperforceGo'' falls under this category. Fortunately, it gave him just enough time to turn his pet monkeys into the Hyperforce. What wasn't shown until "Golden Age" though, was that he was slowly aging. These were his last chilling words as he became Skeleton King:
-->'''Alchemist''': Now, the Dark Ones...''(as Skeleton King)'' take my soul!