Went to a con and roomed with some friends. Went with some other friends to a panel and then to lunch, then went back to my room. Opened the door, entered the room, turned on the lights. My room mates were on the bed, naked, having sex, and they completely froze the second the door opened and I walked in. We all stared at each other for a minute before I walked right back out. We all joked about it and still talk about it every now and then.