I don't post much, but I don't think I've seen this. A bunch of people hold a girl's arms down and others tickle her belly button and stomach. Then they slap her stomach making it red.
http://www.youtube.com/watch?v=uWyrSqo-uJQ&search=belly buttons
http://www.youtube.com/watch?v=uWyrSqo-uJQ&search=belly buttons