Knock-knock jokes (continued)

After a false start, both my kids have the knock-knock joke template down pat:

Speaker 1: Knock knock!
Speaker 2: Who's there?
Speaker 1: [set of words]
Speaker 2: [set of words] who?
Speaker 1: [set of words combined with other words in a way that is designed to make Speaker 2 laugh]

Emily sometimes says "What, [set of words]?!?!?" instead of "[set of words] who?", which can ruin the gag. But otherwise they get great amusement from them. Unfortunately, their appetite is as voracious as their memory is strong. If I'm driving them anywhere in the car, they demand knock-knock jokes incessantly. Not recycled ones from yesterday, but new ones. And let me tell you, it's hard to come up with new knock-knock jokes every 30 seconds.

But occasionally it's worth it. One of Emily's best friends at school is involved in the joke below. See if you can guess her name:

Dad: Knock, knock!
Emily: Who's there?
Dad: Mad!
Emily (concerned): Mad who?
Dad: Madison!!!!!!!!!!!!!

I tell you, if Emily hadn't been in her car seat she'd have laughed herself right onto the road. I think there were three factors leading to this success. First, it was a genuine, simple play on words. Second, the tension of hearing me say "mad" (usually bad news) was palpably eased by turning it into the name of her friend. Yep, funny joke.

Oh, the third thing? Ah yes, the third thing: my daughter is four years old and still thinks anything I say that is supposed to be funny actually is funny. Good times. Enjoy them while they last.

Updated 9/19/7 to fix joke template. I knew something was wrong but couldn't quite put my finger on it.