History Main / MetamorphosisMonster

** ''Series/UltramanGaia'' has a trio of mechanical kaiju called the Nature Control Machines, two of them - Enzan and Shinryoku - which displays morphing abilities, firstly as a giant bell-shaped structure, and then taking on a defensive stance when it's exposed by XIG and attacked by their weapons, before assuming a kaiju form to fight Ultraman Gaia.

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See also {{Metamorphosis}}. Closely related to PupatingPeril.

** The other method is Nymphs, which are flightless, usually aquatic mini-versions of an insect that eventually grow wings and lungs.

* In the SF novel ''The Legacy of Heorot'', human colonists on a new planet find a strangely simple aquatic ecosystem: a kind of fish-analog which they call "samlon" and a genuinely terrifying four-legged predator they call a "grendel." Grendels will eat pretty much anything, so the colonists proceed to kill every grendel they can find on the island where they've settled. A while later, the colony's biologist compares some cell samples of samlon and grendels, and finds she can't tell the difference - because the samlon is the larval form of the grendel. Normally the adult grendels eat the oldest samlon, which are also the closest to metamorphosing into new grendels, but now the adult grendels are all dead...

* Cell from ''Anime/DragonBallZ'' evolves from a half-insect, half-lizard monster to an humanoid android. His intermediate stage is a vaguely humanoid hulk, who for some reason lacks the wing that both his initial and final stage have.

** According to ''VideoGame/MetroidIIReturnOfSamus'', the eponymous Metroids, while on their home planet at least, go from floating parasitic jellyfish to beetlelike creatures to giant armored lizards. In an interesting twist, the first stage is not only the most well-known and arguably most dangerous, but while nearly every game has a variant of the jellyfish stage, the later stages have only appeared in a handful of games as ''VideoGame/MetroidSamusReturns''.
** ''VideoGame/MetroidPrimeTrilogy'': Apparently their larval stage can become mutated in various ways from the chemicals and radiation in its surroundings. Exposing one to Phazon on planet Tallon IV causes it to grow long tentacles, and beta radiation will make it divide into two. They can only complete their normal life cycle on planet SR-388.
** The ''Prime Trilogy'' introduces a whole new line thanks to Phazon exposure. They start as normal larval Metroids before becoming Phazon Metroids that possess IntangibleMan abilities but look almost otherwise the same, then become the Phazon crystal-covered and fully ground-based Hopping Metroids, then regain flight and gain even more Phazon armor and tentacles as a Metroid Hatcher that looks like a floating armored squid. Finally, it's heavily hinted that the titular Metroid Prime is in fact the final stage of this line of Phazon-infected Metroids.

** UF-0 from ''Series/UltramanTowardsTheFuture'', a half-organic, half-mechanical spaceship who starts off as a harmless-looking FlyingSaucer. But after absorbing a rogue scientist who leads an ApocalypticCult, UF-0 suddenly becomes semi-organic, growing crab-like pincers and a tail as well as giant eyes, before flying around and going on a rampage near the Australian coast.

* ''WesternAnimation/AdventuresOfJimmyNeutronBoyGenius'': In the episode "Attack of the Twonkies", the titular creatures are [[RidiculouslyCuteCritter ridiculously cute puffball aliens]] that change into scaly reptilian beasts when exposed to good music, and then physically merge into a huge monster if enough of them gather in one place!

* Most officially defined evolutionary lines in ''Franchise/{{Digimon}}'' fall under this; lines with a consistently maturing appearance are the minority and are generally specifically designed as protagonists of an anime series. Perhaps the standout example is Patamon of ''Anime/DigimonAdventure'', who evolves from a vaguely-defined small orange [[FanNickname flying meatloaf/batpig]] mammal thing into [[OurAngelsAreDifferent an angel]]. In the broader canon, most Digimon have a wide variety of forms to which they can evolve, generally not restricted to specific lines, and so pretty much any and every Digimon can be an example of this.

** UF-0 from ''UltramanTowardsTheFuture'', a half-organic, half-mechanical spaceship who starts off as a harmless-looking FlyingSaucer. But after absorbing a rogue scientist who leads an ApocalypticCult, UF-0 suddenly becomes semi-organic, growing crab-like pincers and a tail as well as giant eyes, before flying around and going on a rampage near the Australian coast.

* A ''WesternAnimation/SpaceGhost'' episode had Jan and Jayce adopt a cute l'il creature called a star fly, unaware that it was the larval form of a giant glowing {{Kaiju}} called a star beast. It grows up fast and seems threatening, but in the end, it remembers Jan and Jayce and refuses to hurt them.

* In ''VideoGame/{{Fe}}'', the young LizardFolk that the eponymous protagonist befriends early in the game look and behave dramatically different from their adult counterparts encountered later on, which take the form of large [[MixAndMatchCritters frilled snakes with manes and antlers]], basically [[OurDragonsAreDifferent serpentine dragons]] or [[SandWorm wyrms]]. Taken a step further with their [[MonsterLord overlord]], who is a [[TurtleIsland mountain-sized]] {{sea serpent}}. The protagonist's species also qualify, resembling hedgehog-flying squirrel hybrids as juveniles, but maturing into [[FoxFolk anthropomorphic foxes]].

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* ''Franchise/{{Godzilla}}'':
** Hedorah in ''Film/GodzillaVsHedorah''. As seen by the image above, he’s actually one of the more grounded examples, since the first few of his forms start off very tadpole-like, then get progressively larger. His Perfect Form is a bit different, being a towering bipedal behemoth, but he retains most of the features of his previous forms, such as large, red eyes and dark green ‘skin’.
** Likewise, there's [[Film/GodzillaVsDestoroyah Destoroyah]] who went from a colony of microscopic crab-things to a giant scorpion-crab thing to a giant demonic crab colossus. The reference books explain this final form as being the result of Destoroyah taking some of Godzilla Junior’s DNA during their fight towards the end of the film’s second act, allowing him to grow an endoskeleton, which in turn enabled him to take an upright body plan and grow much larger.
** [[Film/GodzillaAndMothraTheBattleForEarth Mothra and Battra]], naturally. Both are giant caterpillars who then become giant butterflies.
** ''Film/GodzillaVsBiollante'' has the titular Biollante as another example, going from a giant rose to a bizarre crocodile-Godzilla-rose-tree-[[BuffySpeak thing]].
** And then there's the mutant clone [[Film/GodzillaVsSpacegodzilla Spacegodzilla]] who can switch between his "normal" Godzilla form and his crystal form for long distance travel, in which his legs and tail are completely covered by a huge crystal that connects with his crystal spires on his shoulders.
** Godzilla himself "evolves" over several forms in ''Film/ShinGodzilla'' and ''Anime/GodzillaSingularPoint''.
* Irys from the film ''Film/Gamera3AwakeningOfIrys'' goes from a [[UglyCute strange-looking yet somehow adorable]] snail-like creature with tons of tentacles to a giant bipedal monster with tentacles with spears on the ends, swords for arms, and a cone-shaped head with a single glowing eyeball.

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* ''Literature/InCryptid'': [[OurMermaidsAreDifferent Finfolk]] look just like humans (and can interbreed with them) until sometime in their teens or early 20s, when they start showing scales and turning into merpeople. Exposure to the sea can speed up this change. This also slowly erases their memory of their life on land, and by old age they're little more than non-sapient gigantic fish, which [[MonsterCannibalism won't hesitate to eat their own children or grandchildren]].

** There are also situations where the onscreen evolution is ''not'' the most obvious one from the cards or games. Take Gotsumon, a child-sized RockMonster. In the card games, he has a moderately developed evolution line that consists of {{Palette Swap}}s (he evolves to [[AnIcePerson Icemon]] and [[SpaceMaster Meteormon]]). In [[Anime/DigimonAdventure02 02]], however, he instead becomes the rhino-like Monochromon. Now, Monochromon (Champion-level) has its own PaletteSwap evolution Vermillimon (Ultimate), but in Anime/DigimonFrontier and [[Anime/DigimonSavers Digimon Data Squad]], different Gotsumon appear who evolve into Meteormon, which suggests that Monochromon can branch ''back'' into Gotsumon's Palette Swap line.

* ''Film/{{Gremlins}}'': The Mogwai ''multiply'' if gotten wet, and transform if fed after midnight.

* The Graboids of ''Film/{{Tremors}}'' go through a multi-stage "alternation of generations" metamorphosis similar to the aformentioned Xenomorphs, hatching as slug-like "dirt dragon" larvae, which grow into the familiar bus-sized {{Sand Worm}}s, which spawn numerous bipedal Shriekers sporophyte-style, which metamorphose into the winged, egg-laying Ass Blasters.

See also {{Metamorphosis}}.

** Hedorah in ''Film/GodzillaVsHedorah''.
** Likewise, there's [[Film/GodzillaVsDestoroyah Destoroyah]] who went from a colony of microscopic crab-things to a giant scorpion-crab thing to a giant demonic crab-thing.

** ''Film/GodzillaVsBiollante'' has the titular Biollante as another example, going from a giant rose to a bizarre crocodile-Godzilla-tree-[[BuffySpeak thing]].
** And then there's the mutant clone [[Film/GodzillaVsSpacegodzilla Spacegodzilla]] who can switch between his "normal" Godzilla form and his crystal form of the monsters listed he, Desotroyah, and Hedorah are the only ones, not counting mechs like Super-Mechagodzilla and MOGUERA, that can switch back and forth between forms and they take full advantage of this. Often switching into a previous form and using a different means of attack when head on attacks are proving not useful.
** Godzilla himself "evolves" over several forms in ''Film/ShinGodzilla''.

* In ''VideoGame/{{Fe}}'', the young LizardFolk that the eponymous protagonist befriends early in the game look and behave dramatically different from their adult counterparts encountered later on, which take the form of large [[MixAndMatchCritters frilled snakes with manes and antlers]], basically [[OurDragonsAreDifferent serpentine dragons]] or [[SandWorm wyrms]]. Taken a step further with their [[MonsterLord overlord]], who is a [[TurtleIsland mountain-sized]] [[sea serpent]]. The protagonist's species also qualify, resembling hedgehog-flying squirrel hybrids as juveniles, but maturing into [[FoxFolk anthropomorphic foxes]].

* In ''VideoGame/{{Fe}}'', the young LizardFolk that the eponymous protagonist befriends early in the game look and behave dramatically different from their adult counterparts encountered later on, which take the form of large [[MixAndMatchCritters frilled snakes with manes and antlers]]. Taken a step further with their [[MonsterLord overlord]], who is a [[TurtleIsland mountain-sized]] [[SeaMonster sea serpent]]. The protagonist's species also qualify, resembling hedgehog-flying squirrel hybrids as juveniles, but maturing into [[FoxFolk anthropomorphic foxes]].

* According to ''VideoGame/MetroidIIReturnOfSamus'', the eponymous Metroids of ''Franchise/{{Metroid}}'', while on their home planet at least, go from floating parasitic jellyfish to beetlelike creatures to giant armored lizards. In an interesting twist, the first stage is not only the most well-known and arguably most dangerous, but while nearly every game has a variant of the jellyfish stage, the later stages have only appeared in a handful of games. Apparently their larval stage can become mutated in various ways from the chemicals and radiation in its surroundings[[note]]eg. exposing one to Phazon on planet Tallon IV causes it to grow long tentacles, and beta radiation will make it divide into two[[/note]], and they can only complete their normal life cycle on planet SR-388.

** William Berkin from ''VideoGame/ResidentEvil2'' mutates heavily throughout the game, going from [[DeadWeight a hulking]] [[NotAZombie not-zombie with]] [[EyesDoNotBelongThere an eye in his shoulder]] to a BlobMonster by the end. It took a nuclear blast to finally kill it.

* The Aliens from ''Franchise/{{Alien}}'' also have a peculiar lifecycle: It could be described as [[http://en.wikipedia.org/wiki/Biological_life_cycle#Haplodiplontic_life_cycle haplodiplontic]], with the "gametophyte" being a creature that could be described as a mismatch of hands/legs, tail and genitalia that lives just to seek a host to impregnate, and the "sporophyte" developing in the body cavity of the host, emerging violently as a snake-like creature, and quickly growing up into a large, 4-limbed biomechanoid creature with some traits reminiscent of the host species, but taller and slimmer. If it grows into a fertile queen, it also changes its limb structure, grows an additional pair of arms, increases in size, and loses the host-like characters.