Teaching Grandma

Claire has been trying to teach her Grandma about knock-knock jokes. It's been rather hilarious. This is how their latest conversation went...

Claire: Knock-knock!

Grandma: Come on in!

Claire: No, Grandma. YOU say, "Who's there?"

Grandma: Why do I say "Who's there?" Why not "Come on in"?

Claire: Because that's not how the joke goes, Grandma. Let's try again. Knock-knock!

Grandma: (says nothing)

Claire: You say, "Who's there?"

Grandma: Who's there?

Claire: Boo!

Grandma: (says nothing)

Claire: You say, "Boo-who?" Let's start over. Knock-knock!

Grandma: Come on in!