There’s something about a knock-knock joke. Four-year-olds can’t get enough of them. This is God’s wrath on parents.

I don’t know what crime parents have committed to merit such a harsh punishment, but it must have been something really bad.

Tell a knock-knock joke to a four-year-old (which is something a sane person should never do) and he will assume that you made it up on the spot. Moreover, he will be so enchanted with your improvisational talent that he will begin to search for his own light of inspiration. He will start inventing his own knock-knock jokes, on the spot, just like you did.

Now, because you are insane, you are stuck with a four-year-old knock-knock joke salesman. You will be bombarded with impromptu nonsense, of which all you will understand are the words: “Knock. Knock.” And you will laugh. There is nothing funny about this; you will laugh nonetheless. You will laugh because you don’t have the heart not to laugh, and because you feel awkward about telling your kid to just shut up in public. Also, you are insane. It is mostly insane people who go around laughing when nothing funny is tickling their senses.

I, too, am insane. I did the unthinkable and told my son a knock-knock joke one carefree afternoon. Now, I endure marathons of comedy like this:

“Knock. Knock.”

“Who’s there?”

“Banana.”

I was wondering if you were interested in a free estimate for house painting.

“Banana who?”

“Banana open the door.”

For God’s sake, open the door! I’m getting ripe out here waiting.

And I laugh. I laugh heartily, as though my tin foil helmet is tickling the base of my neck. I laugh like I’ve finally gotten the straitjacket broken in so it doesn’t pinch like it used to do.

The other night, I was enduring a bombardment of such jokes when my son proved that at least one of us still clings to a tenuous grasp on sanity. Somehow, he hit upon the perfect knock-knock joke for a four-year-old. It summed up everything in five lines. It would have been a miserable failure of a joke if it had come from the mouth of anyone even a few years older. For a four-year-old, it was perfect – perfectly funny – because great humor is rooted in truth.

“Knock. Knock.”

Who’s there?”

“I.”

“I who?”

“I have no idea what’s going on here.”

For a fleeting moment, I took off my straitjacket, exited my rubber room, and laughed at the most sanely funny thing in the world: truth.

Then, the normal barrage resumed, and I took shelter in my safe place.