No Pants Party

A close friend of mine and local church worker recently invited me and my husband to a "No Pants Party". The invitation was VERY specific to the fact that NO undergarments of ANY kind be allowed underneath whatever is used to wrap yourself in. Of course, I am VERY surprised to get such an invite from her, considering the church position she shares with me.
I wanna know what exactly goes on at these kind of parties. Do guests generally insist on proof of no undergarments? It`s way too easy to assume that there`s a set up for people to see body parts that they normally wouldn`t, and/or that more kinky stuff could result from it.
I`ve been told from a church counselor that there are supposedly active Christians in our congregation who are having "Key parties" (place your keys in a hat and go home for the night with whomever the owner is of the set you draw out) as well. He gave no names or hints of who he was referring to, but my friends kept coming to my mind and I kept trying to shake it off.
After getting this other invitation recently, I am wondering if the NO Pants Party is similar in any way and if I`m right in connecting this. Can anyone tell me what occurs at this kind of party? I don`t want to jump to any unnecessary conclusions about my friends, but it raises a BIG red flag, considering the morals and standards we preach together.