Rose Tyler: When you say 900 years...

Doctor: That's my age.

Rose Tyler: You're 900 years old.

Doctor: Yeah.

Rose Tyler: My mum was right. That is one hell of an age gap. Every conversation with you just goes mental. There's no-one else I can talk to! I've seen all that stuff, up there, the size of it, and I can't say a word. Aliens and spaceships and things... and I'm the only person on planet Earth who knows they exist.