Episode 3 Under the Lake

Clara: What are they?
The Doctor: I haven't a clue. Isn't it exciting?

The Doctor: The weird thing is, they're not violent. They're too cowardly. They wouldn't say boo to a goose. More likely to give the goose their car keys and bank details.

The Doctor: So who's in charge now? I need to know who to ignore.

The Doctor: It's okay, I understand. You're an idiot.

The Doctor: So, we are fighting an unknown homicidal force that has taken the form of your commanding officer and a cowardly alien, underwater, in a nuclear reactor. Anything else I should know? Someone got a peanut allergy or something?

Pritchard: I imagine they're pretty valuable.
The Doctor: What?
Pritchard: I mean, powerful. Those power cells, I imagine they're pretty powerful.
The Doctor: Well, they can zap a vessel from one side of the galaxy to the other, so yeah, take a wild stab in the dark.
Pritchard: And the missing one must still be out there.
The Doctor: Yes, well, otherwise... sorry. Why is this man still talking to me?

The Doctor: I like adventures as much as the next man, if the next man is a man who likes adventures.

The Doctor: Surely just being around me makes you cleverer by osmosis.

O'Donnell: What we looking for, exactly?
The Doctor: Something that has the power to raise the dead and turn them into transmitters. I except we'll know it when we see it.

The Doctor: Why don't I have a radio in the TARDIS?
Clara: You took it apart and used the pieces to make a clockwork squirrel.

The Doctor: Two weeks of "Mysterious Girl" by Peter Andre, I was begging for the brush of death's merciful hand."

The Doctor: My god. Every time I think it can't get more extraordinary, it surprises me. It's impossible, I hate it, it's evil, it's astonishing. I want to kiss it to death.

Bennett: Wait, you're going to go back in time? How do you do that?
The Doctor: Extremely well.