My wife was at a friend's house yesterday and busted our four year old bouncing on their bed (and ringleading his little brother and the friend's little girl).
He was sternly instructed not to jump on people's beds, and obediently came into the loungeroom.
Several minutes later, my wife hears similar sounds coming from the bedroom and finds our four year old back on the bed.

In straight-faced innocence, he explained that it was okay because he was jumping off the bed.