What's a Joke??

Conversation while I was getting some baking done:

Ace: I've got a joke.

Zoe: Ace, you don't know what a joke is. Do you know what a joke is?

Ace: No.

Zoe: It's when you say, "Ya get it?"

Ace: Oh.

Zoe: Like when you say, "A penguin and a frog...ya get it?" That's a joke! Ya got it?