This happened back when I was 15 years old. I was at my friends house and his sister was there with 2 of her girlfriends. My friend is a year younger than me so he was 14 and his sister was 17 and her friends were 17 years old too. The parents were out and we were all playing together. One of the sisters friends got up and danced and then suggested we all get up and dance individually and take some clothes off. My friend and his sister were not willing to do it but me and the other friend were at least willing to somewhat go along with it. The friend said we didn't need to get naked but just maybe strip down to our underwear. My friend and his sister agreed to at least give it a little try. The girl who suggested to this hot up first and danced and stripped down to her bra and panties. The other girl got up and danced down to her bra and panties too. My friends sister went next and she took her jeans off but kept her shirt on. Her shirt was long so you couldn't see much of her panties. I went next and I stripped down to my underwear. My friend was last and he took his shirt off but nothing else. It came time for round 2 and both my friend and his sister refused to dance again and even put the clothes they took off earlier back on again. The girl who suggested doing this danced again and she flashed us her boobs and then took her bra off altogether. The next girl went again and the other girl tried to get her to flash us her boobs but she refused. After a little more urging she gave us a quick flash but kept her bra on. It was my turn and I got up again. I mooned the others a few times but really surprised them when I took my underwear off altogether. It was unlike me to ever do something like this but with seeing the one girl topless I just got the urge to do it. I was dancing naked in front of them all. My friend and his sister were completely shocked. I finished and the topless girl got up and danced again. This time she took of her panties and was just as naked as me. The other girl refused to dance again so me and the naked girl danced naked together. I remember our dance was more just touching ourselves, and each other, and it mostly being exposing ourselves to the others than any actual dancing. Afterwards the others were completely in shock with how of us they saw and how we were touching each other and ourselves in some rather sexual ways. We remained naked for almost an hour before we heard the parents coming home and quickly got dressed.