Once when I was in college, a super sheltered friend of mine (who lived at home with very strict parents) came to visit me. She wanted to go out and have a good time, so a few of us get together to pregame, call a taxi, and head downtown. Once we arrive, we find that literally all of the 18+ clubs aren't open past midnight. So after an hour of searching around, we decide to settle for like a strip club or something, and start calling all of the nearby clubs listed on yelp. Finally, after several attempts, we find that there's a nearby "swinger's club" that's 18+ and stays open til 4, and we figure, that's practically the same thing as a strip club, right? Wrong.

So when we enter, we quickly learn that the point of the club is for random people to have sex on the spot, and the rule is that everyone who comes in has to strip down to lingerie (if female) or be completely nude (if male). So at this point, my sheltered friend is really desperate for a good time, so who are we to deny her that? So, we go in, and my friend starts mingling, while the rest of us, who were in relationships at the time, are awkwardly avoiding eye contact with the sausage fest that was that swinger's club. There was porn playing on the flatscreens and the patrons were just casually fapping away by themselves. There was a chorus of sound coming from the upstairs bedrooms. There was a threesome happening on one of the couches coated with questionable stains. My friend is just about to score, but after only 10 minutes, everyone ends up randomly getting kicked out of the club for no reason.

My friend, who is upset, begs the bouncer to let us back in, and they eventually agree to it, as long as we don't bring our phones with us (wtf?). So we come back in so our friend can get some, but the other girl we came with starts getting very sketched out, understandably, and decides to wait in the car. I decide to stick around to make sure my other friend is safe, as the bouncer is making generally creepy and rapey comments at this point. My friend ends up having her fun, but I have to endure the weird sex sounds from a distance, as the bouncer occasionally asks me very creepy questions about whether or not I am a "screamer".

TL;DR: My friends and I accidentally end up in a random swinger's club in which all the patrons are naked, and are engaging in orgies or masturbating to porn.