My son asked why I always put the car in park but leave the engine running while I run back inside for his backpack

Look, we had momentum. We were in the car, buckled, ready to conquer the carpool lane. Then someone remembered his spelling homework was still on the counter.

So I put it in park—safety first, obviously—but left it running because hope springs eternal. Maybe this time it'll be a quick grab. Maybe this time we won't also need his water bottle, his library book, and that permission slip I signed in my sleep.

Punchline

I told him it's called "optimistic idling."