4. Head-Spinning Animatronics
An all-time classic of the horror genre, William Friedkin's The Exorcist continues to terrify audiences to this day, and Linda Blair was much-praised for her startling performance as Regan. However, she had a little more help than you might have expected in achieving the duality of innocence and creepiness; not only was make-up employed to convey the toll the possession has taken on her body, but a complex animatronic was used for the more physically challenging possession scenes, notably the one in which Regan's head spins around. That's not to say we expected that Linda Blair did the physically impossible feat for real, but seeing Blair and the puppet together - and specifically, how false the puppet looks without proper cinematic lighting and so on - completely destroys the illusion that we're looking at an actual human face when the head spins. That said, those cold, dead eyes do add to the creepiness.