The Doctor: I'm looking for a ghost.
Alec Palmer: And you are?
The Doctor: I'm the Doctor.
Alec Palmer: Doctor what?
The Doctor: If you like.
The Doctor: Oh. Oh look. Oh lovely, the ACR 90821. Oh, bliss. Nice toggle switches. Ooh, I do love a toggle switch. Actually, I like the word "toggle." Huh. Nice noun, excellent verb.
Clara: Say we actually find her. What do we say?
The Doctor: We ask her how she came to be. Whatever she is?
The Doctor: Because I don't know. And ignorance is... umm, what's the opposite of bliss?
The Doctor: Yes. Yes, Carisle. Ignorance is Carisle.
The Doctor: Do you feel anything?
The Doctor: Your pants are so on fire.
The Doctor: What do you think?
Clara: Uh, color's a bit boisterous.
The Doctor: I think it brings out my eyes.
Clara: Makes my eyes hurt.
Clara: I mean, one moment you're in 1974 looking for ghosts. But all you have to do is open your eyes and talk to whoever is standing there. To you I haven't been born yet. And to you I've been dead a hundred billion years. Is my body out there somewhere, in the ground?
The Doctor: Yes, I suppose it is.
Clara: But here we are, talking. So I am a ghost. To you, I'm a ghost. We're all ghosts to you. We must be nothing.
The Doctor: No, no. You're not that.
Clara: Then what are we? What can we possibly be?
The Doctor: You are the only mystery worth solving.
The Doctor: Listen, all I need to do is dive into another dimension, find the time traveller, help her escape the monster, get home before the entire dimension collapses, and Bob's your uncle.