The first time my wife and I had a sexual experience comes to mind.
We were sitting in my dorm room waiting for some friends to come over, and we had been talking about sex. I was getting downright horny, and I could tell she was a bit interested in seeing me naked, as I am almost the opposite of her ex (he was small, dark, and circumcised. I am the complete opposite). It was just too bad we didn't have any condoms. I mentioned a few options, and I asked her how she liked the idea of me fucking her beautiful breasts. For some reason, she liked that idea best, but then our friends knocked on the door. We quickly straightened our clothes and let them in, and we started chatting a bit. Our friends decided they would go an get some snacks and a movie, and the get back to us. Once they left, we knew that we only had a few minutes, so we got only half naked, and I rubbed myself between her breasts as if there was no tomorrow

. We barely managed to clean up our mess when our friends came back, and I am almost certain that they could tell that something had happened.