Thanks, Moonist! It sounds like your wife's family was more open about nudity than mine was. My sister and I weren't too embarrassed to be seen naked by the other as long as it was just a fleeting glimpse, or we made a good-faith effort to cover ourselves, but not for any extended period of time. Same went for our parents.
We did do a few naked forfeits with friends, similar to your story. It was usually either a card game or Mario Kart, and the winner got to make the loser do a dare. Two times she made me run through the room naked (once uncovered, past her and two of her girlfriends). I made her go topless except for two Harry Potter books, and do a sexy dance in front of her friends, including a couple guys. She actually hammed it up by turning her back and tossing away the books before walking out of the room. Another time I made her and a friend of hers do a naked lap in the pool when they lost a team game. And in front of my friends, I didn't make her get naked, but I did make her serve us snacks in her underwear.
The most female nudity was actually a friend of mine. When she lost, we were going to make her do a naked run, but she asked us if she could do double-or-nothing. And she lost again. So she had to do a fully naked lap around the back yard, no covering allowed. That was pretty sexy, actually. She had the most fiery red bush...