What can I say? I'm easily amused.
Knock knock.
Who’s there?
Cows go.
Cows go who?
No silly, cows go moo.
Knock knock.
Who’s there?
To.
To who?
To whom!
Knock knock.
Who’s there?
A broken pencil.
A broken pencil who?
Never mind, it's pointless.
Knock know.
Who’s there?
Theodore!
Theodore who?
Theodore wasn't open, so I knocked!
Knock knock.
Who’s there?
Little old lady.
Little old lady who?
I didn't know you could yodel!