The Doctor: I've seen bigger. Clara: Really? The Doctor: Are you joking? It's massive!

People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff.

The trouble with a series as it gets older is it can feel like a tradition, and tradition is the enemy of suspense, and it's the enemy of comedy. It's the enemy of everything, really. So you have to shake it up.

Time travel is always more magical somehow when you go into the past. Traveling into the future is something you do, every day. You're just not going to get very far. So, I rather like the past travel.

We're all stories, in the end.

You know when sometimes you meet someone so beautiful — and then you actually talk with them, and five minutes later they're as dull as a brick. But then there's other people, and you meet them and you think: "Not bad, they're okay," and then you get to know them, and their face sort of becomes them, like their personality's written all over it; and they just — and they turn into something so beautiful.

Reinette: One may tolerate a world of demons for the sake of an angel.