spinning The scenes where the possessed Regan's head rotates 180 degrees so that she appears to be looking directly backwards drew significant notice from audiences and critics when the film was released. "All I can tell you is that the way you think I did it is not the way we did it," Friedkin told Castle of Frankenstein at the time. Like other special effects in the film, it was performed live in front of the camera. A life-size animated dummy of the character was built, one so realistic that Blair felt uncomfortable in its presence. Critic Mark Kermode says the scene's impact results from the audience not having expected it so soon after the crucifix scene. He believes its recurrence later in the film, during the exorcism scenes, was added on set since it is in neither the novel nor the screenplay. Blatty had argued against it, telling Friedkin "supernatural doesn't mean impossible", which led Friedkin to insert a shot of Karras, suggesting the scene might just be a hallucination. When audiences reacted strongly to it, Blatty said Friedkin had "prov[ed] me an idiot once again." Special effects supervisor Marcel Vercoutere built the dummy, primarily of latex based on casts of Blair's body, with help from makeup artist Dick Smith. They tested its realism by putting it in the front seat of a New York City taxicab and, when enough people were looking, turning the head. They had given the dummy's face the capability to move and appear to speak, even adding a condom so its throat would bulge when speaking, but it still did not quite look real in the bedroom set. Then Roizman noted that unlike the other characters in the scene, it did not exhale, so its breath was not visible in the chilled air, and a tube was added for simulated breathing, which produced the requisite clouds of vapor. Crucifix scene The scene where the possessed Regan masturbates with a crucifix was filmed with Dietz playing the character since Blair was too young. To make it seem bloody, she struck it against a sponge soaked in stage blood that had been taped to her stomach. Dietz and Friedkin had a lengthy discussion before filming it about exactly how she was to move her arm. "[H]is method wasn't correct, well, anatomically speaking", she recalls. "We had this long discussion about the right way to jerk off