I was at either at my Mother's birthday party or parents anniversary I don't remember what it was exactly. They invited a bunch of friends over though and most of them were drinking. At some point two guys and a girl show up, one of the guys and the girl work with my mom and the third guy is just a friend of the other two. I'm not 21 and I had a friend over so me and him were just laughing and having a good time socializing with the silly drunk people. We didn't realize until after the party but the two guys and the girl had taken some kind of drug before coming over, one guy ended up sitting at a table just looking half dead, while the other guy and girl (who aren't a couple) kind of disappeared. This party took place in a big yard and it was already dark but they have snuck off, only about 10 feet from the lit area of the party and had laid down in the grass. There was karaoke so my dad said several times over the loud mic for them to get back over where everyone else was, he didn't want anything weird going on at the party, everyone was pretty drunk or at least a little buzzed at this point. My friend and I are just laughing it up being what I would say was really dumb and making snide immature jokes about about how they might try to have sex over there. Once a few more comments were made to tell them to get back to the party area and no funny business, I went over to see what was going on. I was laughing it up, snickering and such because I'd never seen someone trying so poorly to lay in knee high grass and play it off that they weren't doing anything. Last time I went to check on them only a few minutes after this whole thing started, they were laying in a spooning position and the girl had her pants pulled down showing her bare ass. I was still chuckling because me and my friend were very immature like that but I quickly report it to my dad. The situation eventually escalates, a small fight happens between my drunk dad and the guy trying to get laid at the party. It wasn't until the next day that I realize how badly that could have gone for the girl. My mom later explained that the girl was in no way involved with the two guys and they were all just coworkers. Tl;dr Stopped a guy from taking advantage of a girl on drugs at my parents party while giggling like a little kid.