Alastor Moody: I'll teach you to curse someone when their back is turned! You stinking, cowardly, scummy... back-shooting...

Minerva McGonagall: Professor Moody! What are you doing?

Alastor Moody: Teaching.

Minerva McGonagall: Is that a...? Is that a student?

Alastor Moody: Technically, it's a ferret.