SARAH: Just how big is the TARDIS?

DOCTOR: Well, how big's big? Relative dimensions, you see. No constant.

SARAH: That's not an answer.

DOCTOR: How big are you at the moment?

SARAH: Five four, just, and that's still not an answer.

DOCTOR: Listen, listen. There are no measurements in infinity. You humans have got such limited little minds. I don't know why I like you so much.

SARAH: Because you have such good taste.

DOCTOR: That's true, that's very true.