Knock knock. Who's there? Silence.

Knock knock. Who's there? Egg

Egg who? Egg-cuse me, I'm cracking under the pressure to make a good joke.

Knock knock. Who's there? Cows go.

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

Knock knock. Who's there? Donut.

Donut who? Donut even think about leaving me out here!