My cat was asleep on my lap as I was sat watching TV one evening. I started to drift off as well...
...then all of a sudden he used my balls as a trampoline and jumped head first into the closed kitchen door.
I screamed due to the immense ball pain, he bounced off the door, rolled several times on the floor, came to rest on the other side of the room, paused for a few seconds looking around as if he'd lost something and then just started cleaning himself.