My 4 yr old was following his Dad around the house, talking and laughing. Well, he got a little too close and accidentally goosed Dad. Dad's surprised reaction mixed with my laughter was all he needed. He started trying to goose his Dad at every turn, chasing him around the house. I couldn't stop laughing, so he kept going. Luckily, Dad is a good sport. It's amazing how such small things can keep kids entertained.
Yes, we have taken steps to ensure he does not goose strangers.