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.

I think that sick people in Ankh-Morpork generally go to a vet. It's generally a better bet. There's more pressure on a vet to get it right. People say "it was god's will" when granny dies, but they get angry when they lose a cow.

Mr Lipwig, there's a lady in the hall to see you and we've thanked her for not smoking three times and she's still doing it!

Time is a drug. Too much of it kills you.

There are some things that are more appropriate to a children's than an adult book but there's a huge overlapping area and most kids read an age group up anyway.

Curiosity may have killed the cat, but her's curiosity could have massacred a pride of lions.

He was currently wondering vaguely who Moey and Chandon were.