Got a concussion in a pillow fight. I was in the top bunk in a lean-to at summer camp when I was maybe 13 or 14. Forgetting the low ceiling above me, I jumped to my feet, planning on launching a pillow at someone poking around another bed. Promptly slammed my head into the ceiling, knocked myself out and wound up going to the doctor shortly after. Pretty sure I still have a disc somewhere with images of the small minor brain bleeding I got as a result.
Genies are probably just super bored stuck in their magic lamps, have to get their entertainment when and where they can.