Knock knock. Who's there? An anticlimax.

An anticlimax who? Exactly.

Knock knock. Who's there? Tell me.

Tell me who? No, *you're* supposed to tell *me* who's there. I'm the one who knocked, and now I'm waiting.

Knock knock. Who's there? A pause.

A pause who? No, just a pause. The joke's over.

Knock knock. Who's there? Alpaca.

Alpaca who? Alpaca the suitcase, we're going on vacation!