James: There are ways to tell whether or not Severus Snape is a witch.
Remus: Are there? Do tell us.
James: What do we do with witches?
Sirius: We . . . burn them!
James: And what else do we burn?
Peter: More witches?
James: Good. Now why do witches burn?
Remus: Because . . . they're made out of wood?
James: Good. So how do you tell whether or not Snape is made from wood?
Sirius: Build a bridge out of him!
James: But can you not also build a bridge out of stone?
Peter: Oh, yeah . . .
James: Does wood sink in water?
Remus: No, it . . . floats!
Sirius: Throw Snivellus into the Black Lake!
James: No, no, what else floats in water?
Sirius: Very small rocks.
Sirius: Lead! Lead!
James: The correct answer is: A Duck.