Where's the off button?

What is it with kids and knock-knock jokes? Is it hard-wired into them? Liam went through a knock-knock phase that he hasn't quite managed to get out of, though his jokes are getting a bit more...funny. Ceana, at the ripe old age of almost-three, has begun telling them. It's killing me. She has to mention every. little. thing. that her eyes come across. Here, for your reading pleasure, is an example of our car rides these days:

C: Knock, Knock
Me: Who's there?
C: Car
Me: Car, who?
C: Tree
Me: Tree, who?
C: Raindrop
Me: Raindrop, who?
C: Stick
Me: Stick, WHO?
C: Coat
Me: COAT, WHO?

And on and on, into either infinity or until something else comes along to catch her attention, by which point I am trying not to pull my hair out. And she's giggling like a little maniac in the back seat. If she's not careful, I'm going to make her run like brother:

See what happens when kids aggravate me in the car? I make them run...No, he's actually running because he couldn't follow the rules of no running in the classroom - so he had to run home from the beginning of the development to our house. Perfect consequence to his actions - though his teacher's recommendation was 3 miles. ;0) Ceana's next, if I have to participate in too many more of her "jokes"...