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? Cows go

Cows go who? No, cows go 'moo'

Knock knock. Who's there? Lettuce.

Lettuce who? Lettuce in, and we'll 'romaine' here all night, serving up 'head'-spinning puns until you 'leaf' feeling 'crisp' with laughter!

Knock knock. Who's there? Silence.