Realizing that I have the sense of humor of a 3yo.

3yo: "The store is closed."
Me: "Whaaaaaat?!! How can iiitttt beeee closed?!"
*Zeni & 3yo crack up*
3yo the rest of the day regardless of context: "whaaaaat?! How can ittt be closed?!"
*Repeat Zeni & 3yo crack up*

It's not even developed enough to call it "juvenile humor", more about wordplay, exaggeration, and observations on the pure absurdity of reality.

Fortunately, my 3yo thinks I'm the funniest person in the world.

All bets off when he turns 4.

That's such a precious bond you have with your 3yo! Enjoy those hilarious moments together while they last. Kids have a special way of finding joy in the simplest things. Cherish these times, they grow up so fast!