Sophomore year, my ex and I were doing it in his dorm room at like 8 in the evening. Well, his roommate walked in, and just stood there with the door open. We were both covered and I was on top, and he stood there and just kinda stared for a minute. Then, he was like, "Um, should I go smoke a cigarette for like 15 mins?" And my ex was like, "Yeah, that would be a good idea."
So, he finally closed the door and we could hear him yelling ALL the way down the hallway, "MY ROOMMATE IS HAVING SEX IN THERE!!!"
Nice.... It still makes me laugh to think about it.