DOCTOR: This has been an absolute joy.

DOCTOR: That’s the trouble with grown-ups. They stop believing in things. And they start liking blue cheese.

DOCTOR: Typical humans. The only thing you ever learn from your mistakes is how to make them all over again.

VALARIE: Tell me why then. Why did they have to die?

DOCTOR: So they and countless others wouldn’t die in agony later. So that the universe could heal.

VALARIE: Hmmm. If you were a monster, I’d leave. No, that’s a lie - er - I’d try and stop you. But you don’t sound like a monster.

DOCTOR: Thanks very much

VALARIE: Having to make a call like that. To save a universe that sick. Sounds like you’re a doctor.

BILL: Sometimes he acts like a big kid, but whenever he sees cruelty and stupidity -- which is often -- it's like they... age him right there on the spot.

DOCTOR: That's it, Ponds! Keep up the attack!

DOCTOR: As we learn about each other, so we learn about ourselves.