Iris Wildthyme
Iris is... well, Iris is Iris. Created by the magnificent Paul Magrs, Iris is unique. A "transtemporal adventuress" she has a shady past, has the habit of claiming the Doctor's adventures were her own and she travels the cosmos in a London Routemaster bus that's smaller on the inside than the outside. She is delightfully bonkers and has appeared in novels, short stories and a whole heap of audios. I have been lucky enough to do two short stories for her. If you don't know her, do yourself a favour and read more about her here.