Belly Button party

So today I had a few friends over with their kids. It just so happens that all of those kids were boys except for one 18 mos old girl. At one point during the morning one of my friends looks into the the sunroom to see a few boys jumping up and down with their shirts off. We thought it was funny but then they decided to come out and run around the house yelling Belly Button Party. We thought this was quite creative for a 6,4 and two 3 year olds to come up with. However by the end of the time here it escalated to them all of a sudden running around in just their underwear and socks and one even took it a step further. We had some funny moments but we thought we should probably shut the party down when they were just in their whitey tighties!