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? Who.

Who who? No, YOU'RE asking 'who.' I'm 'Who.'

Knock knock. Who's there? Existential Crisis.

Existential Crisis who? I'm not sure, but the meaninglessness of this joke is a reflection of the void that lies at the heart of our existence.

Knock knock. Who's there? Homer.

Homer who? Homer-ly, who could resist a classic like this? It's an *epic* pun, don't you think?