Look, he said to his imagination, if this is how you're going to behave, I shan't bring you again.

There's one thing you can say for air pollution, you get utterly amazing sunrises.

People were people, even if they had four legs and had called themselves names like Dangerous Beans, which is the kind of name you gave yourself if you learned to read before you understood what all the words actually meant.

Eight years involved with the nuclear industry have taught me that when nothing can possible go wrong and every avenue has been covered, then is the time to buy a house on the next continent.

There's a saying that all roads lead to Ankh-Morpork. And it's wrong. All roads lead away from Ankh-Morpork, but sometimes people just walk along them the wrong way.

There's a lot of science in it, and as Slartibartfast [in The Hitchhiker's Guide to the Galaxy] said: 'I am a great fan of science, but I cannot do a quadratic equation.' I've never, ever been able to do one. I remember one occasion at Warwick University, when Jack and Ian were at their wits' end because I couldn't get it. I felt totally ashamed.

It's not worth doing something unless you were doing something that someone, somewere, would much rather you weren't doing.