Clanger (Doctor Who DoppelClangers)

A member of a pink, mouse-like species with brown hair once stood in the TARDIS while dressed as the Fourth Doctor, complete with scarf and sonic screwdriver, and spoke in a whistle language as the doors opened. (NOTVALID: Doctor Who DoppelClangers)

Behind the scenes
Although not explicitly stated in NOTVALID: Doctor Who DoppelClangers, they were a member of the Clanger species.