All pathogens progress at a rate of maximum dramatic tension.
This usually means that any effect that has already been established to occur or progress at a certain fixed rate or timeframe will suddenly progress much faster if it reoccurs later. In more egregious cases, Headscratchers can ensue — why is the latest vampire victim-of-the-week crawling out of their grave not twelve hours after their burial, when vampires are supposed to wait three days before rising from the dead?
Despite the title, this is not limited to transformation; it can also apply to illnesses or disease (and is probably one reason why Soap Opera Disease lasts forever).
Take the infection rate of a vampire or zombie bite for example: The Red Shirt who was killed in the opening scene will undoubtably be a full zombie when he is discovered five minutes later, but when The Hero's main Love Interest is bitten and infected, she will suffer a painful and slow progression over the course of several hours (or even days!), successfully hiding her infection from the others or fighting it off until the very last moment (usually long enough to say her final goodbyes). But during their Last Stand against the ensuing Zombie Apocalypse, the former love interest bites the Hero's best friend, and like the Red Shirt who was the first victim, he becomes a full zombie within minutes, if not immediately. (And if some Big Damn Heroes don't show up to save the day, Only the Author Can Save Them Now....)
This can be sometimes justified based on the location or severity of the affliction — if a character suffered repeated zombie bites to vital locations (such as near the neck or heart), it's logical that they will progress far more quickly than someone who was merely bitten once on the hand and let go. After all, in Real Life, the progression rate of an illness varies with the nature of the individual pathogen, its concentration relative to the victim's body mass, and how well it can circulate through the victim's bloodstream. But in fiction, regardless of how it is established during exposition, the formula ultimately boils down to the victim's importance in the plot, and whether they were affected near the beginning, middle, or end of the work itself.
- In the Cowboy Bebop episode "Toys in the Attic", Jet gets bitten by the mysterious creature and takes a fairly long time to get knocked out by the toxin. Faye gets bitten a little while later and loses consciousness in about half the time Jet does, which makes sense given how much smaller she is than Jet. Spike, however, who's definitely closer to Jet than Faye in size, gets bitten and loses consciousness almost immediately. Ein also succumbs to being bitten almost immediately, but that's justified because he's a 30 lb dog.
- Post-Crisis, Superman's origin was changed so that his powers developed slowly as he grew up, storing solar radiation in his body. However as an adult, staying away from the sun for a just a few days quickly drained his powers. Even worse, other kryptonian characters ignored this and charged up rather quickly.
- In the Star Wars/Mass Effect crossover Origins, one of the characters has Rape as Backstory. Some of the plot is spent on her recovery from it and her old life as a hedonistic, spoiled Rich Bitch into a helpful, if quiet person with unexpected knowledge in useful areas. In reality, given what is both implied and shown such a process would take far longer than the year or so of in-story time that passes. Her therapist even lampshades this high-speed change, essentially discussing the trope without naming it.
- In Webwork, all those chosen as hosts for the Oni Essences transform at different rates based on evilness and exposure to dark magic (with Viper even lampshading how erratic the rate is):
- Wong's transformation was near complete in hours due to his innate evil and decades as a dark chi wizard.
- Chang's change took days to finish because, while he was evil, he had no background in dark magic. When driven over the edge of rage, his transformation leaps the last part to completeness.
- Elizabeth Hartman's is an odd one. She was possessed early on, but subconsciously suppressed the changes until it exploded like a backed up pipe, from there transforming near totally at an accelerated pace.
- Valmont transformed into the Crab Khan general near totally in one night's sleep. Jade initially thinks it's because he wore that general's mask before, and went through the experience of Sharing a Body with Shendu, the strongest of the Demon Sorcerers, for a few weeks, before coming to the conclusion that Valmont's become so beaten down from his fall from power that his soul didn't even try to resist the change.
- Nivor's transformation is mostly unseen, but it's implied to be pretty quick, as Nivor is only a few minutes away from becoming full Oni when we see him.
- Drew's already started to develop a couple signs of change, namely an extreme hunger that Nivor seemed to share, despite just getting the Essence. However the Essence itself is actively opposed to him becoming a general, as it only chose him out of desperation after being driven out of Nivor.
- Origami also changed most of the way physically in a few hours, which seems to have been, at least partly, a result of the Razor Khan Essence reacting with his (possibly unique) paper magic, which was also affected by the change, becoming more like tinfoil.
- Despicable Me: Hand Waved rather than just played straight. Things shrunk by the shrink ray eventually unshrink, and this is foreshadowed. But the moon unshrinks a mere few hours after shrunk. But, they say that the bigger the object, the sooner it unshrinks. And the moon is extremely big. However there is Fridge Logic in the fact that the minion shrinks before the flyer, when the flyer was shrunk first.
- Beauty and the Beast, mostly in the Broadway musical. The curse has the enchanted objects becoming less human (since, being onstage, they are life-size and somewhat human). This has been happening for ten years, and suddenly they're on the brink of transformation a few days after Belle's arrival.
- The Emperor's New Groove: Kuzco's potion-induced transformation happens gradually, with his body parts becoming that of a llama's one by one. However, every other transformation in the film occurs instantly in a puff of smoke. The former case can be justified a bit, as Kronk mixed the potion with water while preparing it, which probably diluted it and weakened its effects.
- Fantastic Voyage has a 1-hour time limit before the surgical team will begin to regain their original size. In the novelization by Isaac Asimov, the degree to which you are shrunk affects your time at that size. It is stated that being shrunk to half-size would take years to wear off, but the extreme size reduction needed by the team means they only have a single hour.
- The gestation period of xenomorphs in the Alien series. The first film has several hours between the victim getting attacked by the facehugger to the chestburster leaping out, and another several-hour interval before the xenomorph matures. In Alien vs. Predator, a group of people is implanted and the temple is swarming with mature xenomorphs in a matter of minutes. This could be explained by the Predators having bred or selected a line of xenomorphs that had a hyper-accelerated growth rate even by their species's standards, except that the Predator gets infected in the middle of the film and the Predalien chestburster doesn't emerge until the very end of the movie.
- In Blade II, a new strain of vampire virus creates Reapers. The transformation from a vampire to a Reaper is shown early in the movie to take place quickly with considerable pain and Body Horror. However, Lighthammer manages to press on for hours before he finally turns and eats a couple of his teammates, and Nyssa gets plenty of time to watch Blade's fight and then the sunrise.
- The Drow elves in Forgotten Realms. It was established in Drizz'ts' origin trilogy that it took him months to adjust to surface daylight; later drow stories would have them up and about in the sun sometimes almost immediately.
- There's a difference in the time various people sickened and died in The Stand. When the virus is first released inside the army base, everyone is dead in minutes, minus Campion, who makes it about a day before dying. Other people take several days to die, because they get briefly better before getting worse. The TV miniseries Hand Waves this by stating that Campion was exposed to a mutated version of the virus that takes longer.
- Justified in a Get Smart episode where Smart has been poisoned with a toxin that kills in 24 hours. CONTROL's attempts to reverse-engineer it result in a version that kills in sixty seconds, which he uses against the doctor who developed the original poison to acquire the antidote.
- Doctor Who:
- Justified in "The Waters of Mars". The zombie-like infection is actually a microscopic Puppeteer Parasite, and can decide for itself when is the best time to take over its victim.
- Not justified in "Amy's Choice", where the attack that instantly dusted everyone else we saw it hit gave Rory enough time for a tearful goodbye before gradually dissolving. Of course, it was All Just a Dream, so who says it has to make any more sense than a "cold star?" If you watch, Rory is hit with what looks to be a smaller and more indirect dose of the gas, hence he dusted slower.
- In the pilot of Stargate SG-1 the team finds a long list of Stargate addresses, but since the Stargates have drifted since the list was put down, they have to be re-calculated by their computer. Carter states that with this process they can discover two or three new Stargates a month. Of course in a later episode they find a complete and up-to-date map of Stargate addresses and drop that concept.
- The Star Trek: Enterprise episode "Regeneration" has characters infected with Borg nanoprobes transform into drones much more slowly than usual.
- In Kamen Rider Gaim, any living creature wounded by an Invess starts being consumed by parasitic Helheim plants in a matter of hours or even minutes. Late in the series, Baron is injured in battle with an Invess Overlord, but his infection progresses so slowly that he manages to conceal it for many episodes. It's left ambiguous whether this is due to the wound coming from an Overlord, or simply Baron's sheer willpower.
- The protagonists of Final Fantasy XIII are made into l'Cie by the fal'Cie Anima: their Focus mandates that they must destroy Cocoon, or else transform into mindless, shambling Cie'th. Each of them bears a brand that acts as a timer, indicating how long they have left: however, the importance of this time limit is inversely proportional to how determined the protagonists are to Screw Destiny. In the end, it never actually comes into play: the protagonists are apparently transformed into Cie'th during the final confrontation, but it turns out to be just an illusion created by Barthandelus to drive Fang over the Despair Event Horizon.
- In the Adventure Mode of Super Smash Bros. Brawl, the first cutscene depicts Mario and Kirby transforming from trophies to their animate forms toe-to-head. After that, any time a character is revived from his or her trophy state, the transformation is a simple white flash on the screen. If the trophy in question was lying on its side when it happens (which is most often), the character is then shown either getting up or already standing.
- SpongeBob SquarePants: In the episode "Best Frenemies," the Kelpshakes that everyone is drinking give them green shag that covers their entire bodies, but not until the end of the episode. However, Krabs and Plankton, who have been avoiding drinking them for the entire episode, finally drink it before Karen can warn them of the toxic ingredient. The Kelpshake effect happens almost immediately after they discover that everyone else has it.
- In one episode of Disney's Aladdin: The Series, Jasmine was given a mysterious "beauty potion" that actually began slowly transforming her into a naga. Cue a long trek to locate the means to reverse it. Ultimately, Aladdin declares he would rather stay with Jasmine than leave her behind, and uses the potion on himself — with immediate results.
- In one episode of Ben 10, Ben is scratched by a creature who has been identified as the Yenaldooshi by a Character of the Week, and spends half of the episode slowly becoming more and more like it. In the end, it's revealed that it was really nothing more than an alien wolf-like creature, and the transformation was due to a quirk of the Omnitrix that allows it to learn and mimic the form of any alien that touches it. Every other time this ability comes into play in later episodes, the form is added automatically and the transformation is as quick as Ben's usual shape-changing. Handwaved by saying something like it was stuck in-between collection mode and something else, so it caused a gradual change.
- In "Can I Keep It?" on Little Princess, Little Princess's tadpole is shown to have transformed into a frog overnight and visually in the space of about 10-15 seconds. When Little Princess awakes, she believes that the awful creature, which she doesn't recognize as a frog, has eaten her "Taddy". In real life, tadpoles slowly grow legs and gain frog-like features.