People think that stories are shaped by people. In fact, it's the other way around.
I don't think I've drunk enough beer to understand that.
If you put butter and salt on it, it tastes like salty butter.
A number of religions in Ankh-Morpork still practiced human sacrifice, except that they didn't really need to practice any more because they had got so good at it.
Nanny Ogg never did any housework herself, but she was the cause of housework in other people.
You get all sorts of people in the library, and the librarian gets it all.