Most nude/sex scenes in movies are not surprises. The lead couple embrace. They kiss, the music swells. You know what’s coming next, the droppage of clothes, etc. etc. Or the cops or mobsters pull up in the parking lot of the Pussycat Lounge. It’s not surprising that naked women will be dancing onstage in the next scene.
A surprising nude/sex scene is one which gives you no warning it’s coming up, either in the nature of the movie or the way the plot progresses.
One example that springs to mind is Emma Thompson’s scene in, I believe, Howard’s End. At some point one of the characters opens a door to a bedroom, without any buildup at all, and there’s Emma Thompson, stark naked, riding some guy cowgirl style, shagging the living hell out of him. It was quite startling in what seemed to be a droll English tragicomedy.
Another example that springs immediately to my mind is “The Borrower,” a cheesy 90s horror flick about an alien sent to Earth as punishment for some crime or other. The plot gimmick is, he needs to wear the bodies of humans to survive on Earth, but for some reason, the heads of his victims tend to explode periodically. So he has to “borrow” a new head from someone, by ripping it off their shoulders, and placing it on his own shoulders.
Messy process.
Anyway, at one point he grabs a nurse and drags her into a closet in a hospital. Next scene, you see the back of the guy walking out of the closet . Then a shot inside the closet. You expect to see another headless body. Instead, the nurse is lying on a cot face down, completely intact, but stark naked and bound and gagged. The Borrower only wanted to borrow her clothes. The shot lasts for about 2 seconds, and there’s no other nudity in the movie. I’m not even sure it was put there to get an R rating, because since she was face down, there were no naughty bits showing.
In both films, the sex/nudity was a total surprise, and intended to be. Any others like that out there?