When writing comedy, you have to have the confidence to believe that there is only one type of relationship in the world, and we are all having it, that all men behave in the same way and so do all women.

There's something really cool about scaring children. Traumatize a generation, that's what it's all about.

It's the 50th year of Doctor Who and look what's going on! We're up in the sky and under the sea! We're running round the rings of an alien world and then a haunted house. There's new Cybermen, new Ice Warriors and a never before attempted journey to the centre of the TARDIS. And in the finale, the Doctor's greatest secret will at last be revealed! If this wasn't already our most exciting year it would be anyway!

Amy: I had something I wanted to tell him. Stuff always gets in the way. Canton: Stuff does that.

You should always waste time when you don't have any. Time is not the boss of you. Rule 408.

The Doctor: This is bad, I don't like this. [kicks console and yells in pain] Never use force, you just embarrass yourself. Unless you're cross, in which case... always use force! Amy: Shall I run and get the manual? The Doctor: I threw it in a supernova. Amy: You threw the manual in a supernova? Why? The Doctor: Because I disagreed with it! Now stop talking to me when I'm cross!

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.