Metamorph

A metamorph was a lifeform that was able to alter its physical form to match that of another.

Biological metamorphs
Some metamorphs had the ability to take on a wide variety of forms, with few limitations. These included Rutans (GAME: The Gunpowder Plot), Aubertides (PROSE: Human Nature), Brancheerians (COMIC: Meteorite Meeting), Gizou (COMIC: Agent Provocateur), Gwanzulum (COMIC: Planet of the Dead) and Kymbra Chimeras. (COMIC: Changes)

Other metamorphs seemed to be only able to take on humanoid forms, such as multi-forms (TV: The Eleventh Hour) and Vespiforms. (TV: The Unicorn and the Wasp)

Still other metamorphs were limited to shifting between a default form and an alternate form. These included Axons (TV: The Claws of Axos), Carrionites (TV: The Shakespeare Code) and Vardans (TV: The Invasion of Time) Werewolves could change from humans into wolves, while some vampires could change into bats.

Although most metamorphs changed form voluntarily, others could not. Time Lords changed form whenever they regenerated (TV: The Tenth Planet), as did Kastrians (TV: The Hand of Fear). The Yend became involuntary shapeshifters after exposure to radiation from the rogue star Mortain (PROSE: The Sons of the Crab). Mutant humans changed form whenever they touched another living being, becoming identical to the person or Alien they touched (TV: Time Heist).

Technological metamorphs
Some species were only able to change their shape through the use of advanced technology.

Cell 114 sleeper agents were apparently modified to resemble the native species of the planets they invaded, and could change back and forth once they were activated. (TV: Sleeper) The Chameleons used technology to assume the identities of other beings after losing their own. (TV: The Faceless Ones) Usurians exposed themselves to particle radiation to assume humanoid form. (TV: The Sun Makers) Zolfa-Thurans could change the appearance of any humanoid they possessed, but only to a similarly shaped being. (TV: Meglos) Zygons used body-prints to augment their limited natural shapeshifting abilities. (TV: Terror of the Zygons)


 * It is unclear if the Abzorbaloff was a metamorph or merely using technology to disguise himself as a human. Note that the disguises used by Bane, Graske, Raxacoricofallapatorians and Vinvocci were camouflage, not true shape-shifting.