15th DOCTOR: Look after him, you know? Now, you two, if you don't mind, there is a great big universe out there calling, and I've got to get going. So off you pop, old man.

14th DOCTOR: Oh. You're the old man. You're older than me.

DONNA: Actually, that is true. He's younger because you came after him. So you're the older Doctor.

15th DOCTOR: Okay, kid. I love you. Get out!