When I was 3 or 4 my favorite knock knock joke went like this:
Knock knock!
Who’s there?
Ida!
Ida who?
Ida know I forgot my name!

And repeat. Over and over and over and over. I thought I was so clever. I was probably very cute. The first three times. Then I am sure I got incredibly annoying.

Know how I know that?

Because I currently have two little boys who love knock knock jokes. Fritz’s favorite goes like this:
Knock knock!
Who’s there?
Boo!
Boo who?
Don’t cry!

At least he’s gotten to the full joke stage. Adrian loves knock knock jokes, but he doesn’t quite get the entire concept just yet. His go something like this, with variations every time:
Knock knock!
Who’s there?
Fritz!
Fritz who?
Fritz over there!

Indeed.

After a couple dozen knock knock jokes by Adrian and several boo who knock knock jokes from Fritz I start trying to ignore them. Fritz takes the hint, but Adrian doesn’t. Instead he starts saying “Knock knock! Knock knock! Knock knock! Knock knock!” over and over becoming more insistent with each knock.

Think I should teach Fritz the Ida know joke just to give him a little variety?