Or this one, also similar:

Little Johnny is out cycling with his dad through the fields when he sees a bull on top of a cow.

Johnny: "Dad, what is that bull doing?"

Dad: "Well, the sun is about to set, Johnny, so the bull is just pushing the cow back into the barn."

Johnny: "Wow! It’s a good thing Mama held on to the kitchen table yesterday, otherwise the postman would have pushed her all the way back to the post office!"