In addition to Halloween and UNICEF Day, October 31 is National Knock-Knock Joke Day. What better day than Halloween is there to celebrate some of the silliest, most kid-pleasing forms of humor? In fact, if people ask for a trick in exchange for a treat (which they rarely do these days), share a good knock-knock joke.

(Of course, my dad used to make me do this silly trick: I would make a hole with my pointer finger and thumb and ask the person, “Can you poke your head through this hole?” They would of course say no, and then I would say, “I can,” and stick my other pointer finger through the hole and poke myself in the head. The old ladies loved it; otherwise, it was pretty embarrassing.)

Kids love knock-knock jokes. While everyone is born with the potential to have a sense of humor, it still requires development. Telling knock knock jokes helps your child learn about humor, as well as conversation and taking turns. Telling the jokes also helps his or her self-esteem and creativity, which means that it’s very important to listen and laugh to every joke he or she tells—even if it’s for the millionth time!

To introduce your child to a knock-knock joke, start simple. This classic is usually understood by most children:

Knock knock.

Who’s there?

Boo.

Boo who?

Oh, please don’t cry!

Yes, we think it’s lame and stupid, but they love it—and you have to admit, at some point, you probably did too! And though you can Google “kids knock knock jokes” and find thousands of hits, it’s best to keep them as simple (and clean!) as possible for little kids.

Here’s one that my daughter and I love:

Knock knock.

Who’s there?

Police.

Police who?

Police give me a hug!

At four, she’s just become very interested in jokes and cracks up every time we do this one—even though she knows the punch line, and she knows she’ll get a hug at the end.

One of my favorite knock knock jokes is good for older children—and made my husband crack up as, apparently, he’d never heard it before, surprisingly enough:

Knock knock.

Who’s there?

Little old lady.

Little old lady who?

I didn’t know you could yodel!

Of course, seeing as it’s Halloween, you might want to stick with Halloween jokes to tell your children. These can also be a hit at school Halloween parties, during trick-or-treating, or other occasions. Here’s one to get you started that’s particularly good if your kid is a vampire this year:

Knock knock.

Who’s there?

Ivanna.

Ivanna who?

Ivanna suck your blood!