Metamorph

A metamorph was a designation of a lifeform that was able to shift, change or alter its appearance to take on the characteristics and appearance of another species (and then change back).

Examples of such beings include:
 * Werewolves
 * Meglos
 * Krillitanes
 * Bane
 * Graske
 * Vespiforms
 * Raxacoricofallapatorians
 * Prisoner Zero
 * Vampires

The ability of a metamorph could be achieved through technology as well. The Bane used image translators to stay hidden. (SJA: Invasion of the Bane) During the change, morphic residue could be a byproduct, as was the case with the Bane and with the Vespiforms. (DW: The Unicorn and the Wasp)

One of the better known metamorphic species is the Zygons, who could use body-print technology to take the shape of humans. (DW: Terror of the Zygons)

When they needed to get some medical equipment, the Vinvocci used a shimmer to disguise themselves as humans, though the effects seemed to induce a sense of claustrophobia. (DW: The End of Time) Similarly, when members of the Slitheen crime family disguised themselves as obese humans, they suffered from indigestion problems and an uncomfortable need to shed their disguises and be naked; their dialogue would imply that this partially stems from inherent self-admiration. (DW: Aliens of London / World War Three, SJA: Revenge of the Slitheen)

The Abzorbaloff may have been a metamorph since he was able to disguise himself as a human. (DW: Love & Monsters)