Basically in the episode where Basil is putting on a Gourmet Dinner night for the cream of Tor quay,his cook gets drunk and cant cook for them so Basil gets some other guy to cook a duck.As Basil is changing the Menu's from some rich ass food to duck served with about everything you could think of..he starts imitating the sound of a duck.Despite the fact his mouth is shut you can still for a brief few seconds hear the sound of a duck.Watch it and you'll see what i mean.