Knock knock. Who's there? Cows go

Cows go who? No, cows go 'moo'

Knock knock. Who's there? Cows go.

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

Knock knock. Who's there? Sew

Sew who? Sew long, I've been trying to weave a good joke together.

Knock knock. Who's there? Maple.

Maple who? Maple you a favor and open the door!