I was in a fraternity in college, and had just moved into the frat house. I had a nice view from my window, and I like to read while lying in bed, so I had placed my bed along the wall by the window, figuring that this way, I can enjoy the cool breeze and the view while studying. The bed was about a foot lower than the window, and I had blinds, so privacy wasn't an issue.
My room was on the 3rd floor, directly over a large deck on the 2nd floor where people like to hang out, especially during parties. It was during one such party that my gf and I went upstairs to enjoy some private time. We had the lights off, and lit several candles on the floor where we were sitting while smoking. She offered to give me a bj, so we got off the floor, and onto my bed.
I was laying on my back when she got to work. We had the blinds closed, but left the window open to air out the smoke, and for the party atmosphere. After about half a minute, we heard the conversation die down outside, to be replaced by cheering. I was like, "I wonder what's going on out there?" My girlfriend shrugged, looked towards the window, and noticed that the half dozen candles throughout the room were casting a clear silhouette of her head against the blinds. She slowly turned her head towards me, eyes wide in embarrassment, and I noticed that you could see every movement of her head from the shadows on the blinds!
We quickly scrambled off the bed, and blew out the candles. Our fears were confirmed when we heard a chorus of groans from outside, followed by loud booing. We tried to continue in darkness, but found it difficult, both because we were laughing so hard at our predicament, and the chanting of "we want to see!" from outside, so we gave it up and went downstairs.
I got a lot of high fives from guys who knew that it was my room, meanwhile playing innocent with guests who were talking about it. "Dude, you missed it! Some guy was getting a blow job upstairs, and we totally saw the shadow in the window! Where were you?" "Um, I was, ah, getting a keg from the basement..."
We rearranged my room the next morning.