Metamorph
From TARDIS Index File, the free Doctor Who reference.
A metamorph is a being which is able to shift or change or alter its appearance to take on the characteristics and appearance of another species (and then change back).
Examples of such beings include:
The ability of a metamorph can be achieved through technology as well. The Bane used Image translators to stay hidden. During the morph process, morphic residue can be a byproduct, as was the case with the Bane and with the Vespiforms.
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)
