Shapeshifter

A shapeshifter was a being imbued with the ability to alter its physical form. (COMIC: The Shape Shifter)

Frobisher, the Whifferdill companion of the Sixth and Seventh Doctors, frequently used his species' shapeshifting abilities on their travels. (COMIC: A Cold Day in Hell!, Frobisher's Story, Changes) Frobisher fell ill with mono-morphia, which took away his ability to shift, leaving him stuck in the form of a penguin. (COMIC: Genesis!) He recovered enough to shift into various forms while battling another shapeshifter, a Kymbra Chimera, aboard the Doctor's TARDIS. (COMIC: Changes)

After leaving the Doctor, they met again when the Time Lord was in his eighth incarnation. However, as Frobisher had taken a humanoid form and was known as Bish, and the Doctor had regenerated, neither recognised the other. (COMIC: Where Nobody Knows Your Name)

Members of the Rutan Host could shapeshift into other forms, but they needed to know the form very well, usually after careful study and dissection. On Fang Rock in the 1900s, a Rutan killed Ben Travers so that it could later take the shape of Reuben. (TV: Horror of Fang Rock)

Nostrovites were shapeshifting carnivores. A number used this ability to infilitrate the wedding of Gwen Cooper and Rhys Williams in order to extract the unborn Nostrovite from Gwen's womb. (TV: Something Borrowed)