My son called out from his bed, asking for a drink, so I went and got a bottle from the fridge, since I was still up. When I got to his room, he was lying on his back (oozing a deliberate innocence, as it turned out) with his hands behind his head. This left his armpit naked and exposed.
No, I didn't resist. One cold bottle of water in the armpit later and he's giggling rather more than I expected.
Then, I shuffled off to my bed (without turning on the light. I know my room) laid down and discovered the little scamp had stolen my pillow.
I think we are even for the evening.