On the way to VBS at church, Keely told a knock-knock joke:
Keely: Knock-Knock
Me: Who's there?
Keely: Ken
Me: Ken who?
Keely: Ken I come in?

Kai wanted in on the jokes so he said:
Kai: KJ, knock-knock
Keely: Who's there?
Kai: Kai
Keely: Kai who?
Kai: It's Kai.

Chris and I started laughing and Keely said, "That didn't make any sense, Kai. That's not funny."

Kai said: KJ, knock-knock
Keely: Who's there?
Kai: Kai
Keely: Kai who?
Kai: Kai on a horse.

We busted out laughing again and Keely said, "I don't understand why you are laughing? That wasn't funny and I'm not laughing, so why are you laughing?"

Ooooh, how I forgot about kid knock-knock jokes...