Most of the time I tell my pupils that there is no such thing as a stupid question, however recently I found someone who without doubt obviously thought about it and decided it was a challenge and not just a statement.
I'll set the scene we were parked in a side road facing down towards the local beach, right opposite a slipway which lead down into the water.
His question was "what would happen if I drive the car down the slipway into the water?"
I responded with "you'd get hurt and if the water didn't do it, you'd get hurt".
I've never said "there's no such thing as a stupid question" again.