Knock-Knock

I've been trying to teach Z a knock-knock joke – G and BB have been memorizing a new joke every week to tell friends at church –, specifically the one that goes, "boo, who?", "don't cry, it's only a joke." She's finally got the beginning down, but then she gets distracted or the elements get out of sequence, so that you either never get to hear the punchline or the punchline comes before its time. But then her innovations can be quite amusing, like, "Who's there?... A joke!"