Ruby and The Doctor in “Space Babies”

Who are you?

I'm the Doctor, you don't have to stand over there, come and have a look, it's called the TARDIS.

Ooh! nice, but hold on, I can't call you doctor, no I want to know your name.

Yeah that's uh, that's tricky, because I was adopted and the planet that took me in, they were kind of... they were kinda posh, they'd use titles like the Doctor, or the Bishop, or The Rani or the Conquistador, say doctor for a thousand years and it becomes my name