Knock knock. Who's there? Dwayne

Dwayne who? Dwayne the bathtub, I'm dwowning!

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? Silence.

Knock knock. Who's there? Cows go

Cows go who? No, cows go 'moo'