Must Have: A Store of Knock-Knock Jokes

My son has just gotten to the age when he wants to tell and hear knock-knock jokes several times a day. Any parent of a five-year-old needs a good store of knock-knock jokes. Right? I know I'm not the only parent of a five-year-old who has run into this.

I ran out of knock-knock jokes.

So I went hunting online and this site has a few good ones in the comments. It's not a joke site but it yielded some good results for my challenge.

One of my favorites from that site - because my son actually gets it instead of just laughing because he thinks we're being silly - is this one:

"Knock knock."

"Who's there?"

"Interrupting cow."

"Interrupt-"

"MOOOOOOOOOOO!"

My personal favorite - because I could remember it when my son suddenly wanted to do knock-knock jokes - is this:

"Knock knock."

"Who's there?"

"Boo."

"Boo who?"

"Please don't cry, sweetheart!"

The orange-you-glad-I-didn't-say-banana one is appreciated but not understood around here.

This site has lots more knock-knock jokes that children would find funny, though maybe not adults.