DOCTOR: (Blithely) Yes, I imagine so. It's quite clear that Frederick brought the car into the house, ran himself over with it, and put it back outside before he finally expired

ACE: But when?

DOCTOR: Are you looking for the butterfly?

ACE: What the one who beats its wings and tips the balance, so the hurricane forms? There isn't one, is there?

DOCTOR: Not often. They just tell the butterflies that to keep them happy.

ACE: I should have known.

DOCTOR: No, mostly they break the butterfly on the wheel of time. But over the decades, the millions of butterflies, the weather still changes somehow. That's time. A million, multi-coloured pieces of time.

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

DOCTOR: You wanted advice you said. I never give it, never. But I might just say this to you. Always search for truth. My truth is in the stars and yours is here.

DOCTOR: I tolerate this century, but I don't enjoy it. Have you ever thought what it's like to be wanderers in the fourth dimension? Have you? To be exiles? Susan and I are cut off from our own planet, without friends or protection. But one day we shall get back. Yes, one day. One day.

DOCTOR: Fear makes companions of all of us.

DOCTOR: If you could touch the alien sand and hear the cries of strange birds and watch them wheel in another sky, would that satisfy you?