Every procedure for getting a cat to take a pill works fine - once. Like the Borg, they learn.

You were the kind of kid who couldn't see the difference between throwing rocks at a cat and setting it on fire.

"There's a door," he whispered. "Where does it go?" "It stays where it is, I think," said Rincewind.

Monsters are getting more uppity, too (...) I heard where this guy, he killed this monster in this lake, no problem, stuck its arm up over the door (...) and you know what? Its mum come and complained. Its actual mum come right down to the hall next day and complained. Actually complained. That's the respect you get.

Humans can think inhuman thoughts.

He helped the Librarian up. There was a red glow in the ape's eyes. It had tried to steal his books. This was probably the best proof any wizard could require that the trolleys were brainless.

You can't remember the plot of the Dr Who movie because it didn't have one, just a lot of plot holes strung together. It did have a lot of flashing lights, though.