That's the other Monty Python scene:
CROWD: A witch! A witch! A witch! We've got a witch! A witch! VILLAGER #1: We have found a witch, might we burn her? CROWD: Burn her! Burn! BEDEVERE: How do you know she is a witch? VILLAGER #2: She looks like one.
I weigh a lot more than a duck, so maybe I'm safe...