Woman Discovers She’s Screwing an Alien, in They Live (1988)

John Carpenter makes the top spot, as well, for this very different human-alien sex scene that closes out his cult sci-fi flick. Hopefully this isn’t a spoiler for anyone, but at the end of the movie, Roddy Piper disables a broadcast signal that makes the alien invaders look human. Following this, we see a short montage in which these creepy-looking aliens are suddenly revealed as such to the people around them. The final shot is the most hilarious, though, as it involves a woman having sex with what she thinks is a man. She looks down and sees she’s straddling an alien, who gets the film’s last line: “Hey, what’s wrong, baby?”