Anything and everything; they can change their exterior appearance to blend in with their surroundings. Except for mine, that is. [He secretly likes it that way. Shh.]

Naaaah. We evolved like this before we ever developed time travel, and the TARDISes are bigger on the inside, so fitting isn't much of a concern. Most of my people are traditionalists; they keep to humanoid bodies 'cos that's what we've always done. It's just easier that way.