Knock knock. Who's there? Vaughn.

Vaughn who? Vaughn voyage! Hope your journey's ship-shape and full of bon-bons!

Knock knock. Who's there? Pane

Pane who? Pane-de-monium, I'm having a window of opportunity to tell you a glass-half-full joke!

Knock knock. Who's there? Cows go.

Cows go who? No, cows go 'moo'.

Knock knock. Who's there? Alpaca.

Alpaca who? Alpaca the suitcase if you open the door!