Knock knock. Who's there? Wu

Wu who? Wu don't know, it's a Chinese puzzle to me, but I'm paws-itive I'll figure it out, fur-get about it!

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?

Knock knock. Who's there? Waiter.

Waiter who? Waiter minute, I thought *I* was supposed to be asking who's there!

Knock knock. Who's there? A placeholder for a name.

A placeholder for a name who? Exactly. It could be anyone, couldn't it?