Knock knock. Who's there? Hearse.

Hearse who? Hearse a real groaner for ya: I used to be a baker, but I couldn't make enough dough to roll with the big timers!

Knock knock. Who's there? Recursion.

Recursion who? Recursion who? Knock knock.

Knock knock. Who's there? Parenthesis.

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.