Knock knock. Who's there? Someone.

Someone who? I don't know, I just heard a knock.

Knock knock. Who's there? Lettuce.

Lettuce who? Lettuce *pray* this joke *grows* on you, I've really *leafed* through a lot of ideas to *cultivate* this *gem* just for you, so please *romaine* here and enjoy!

Knock knock. Who's there? Alpaca.

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

Knock knock. Who's there? Cows go.

Cows go who? No, cows go 'moo'.