Knock knock. Who's there? Tank.

Tank who? Tank you for opening the door!

Knock knock. Who's there? Egg

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

Knock knock. Who's there? Wu

Wu who? Wu don't know, I'm having an identity crisis!

Knock knock. Who's there? The joke.

The joke who? The joke who was supposed to be original and unexpected, but now feels like it's just pointing out its own existence.