Veronica Cartwright in Alien (1979)
The chest-bursting scene from Alien ranks among the most iconic moments in all of sci-fi film history, and perhaps that’s partly because the cast involved in the scene really didn’t know what was about to happen to them on the set and were genuinely disturbed by it. Director Ridley Scott explained his reason for letting the creature’s big reveal happen in real-time during the shoot, saying, “The reactions were going to be the most difficult thing. If an actor is just acting terrified, you can’t get the genuine look of raw, animal fear.”