she giggled a little bit. "Have you ever done that?" he asked. "Sure; haven't you?" she responded. She was cast after tests with Burstyn; Friedkin wanted to keep that level of spontaneity on set. "After all these difficult scenes she'd tiptoe around and giggle, after every bit", Blatty recalled. "It was all a big funhouse ride for her. She was disturbed only one time, and that was when her pet mouse died." After filming, Friedkin had similar praise: "She is the most totally pulled together, stable, mature young person I've ever met. The whole thing was a game to her." Of the 500 actresses he said he saw audition, "there wasn't one other I would have considered." Friedkin originally intended to use Blair's voice, electronically treated, for the demon's dialogue. He felt this worked fine in some places, but the scenes with the demon confronting the two priests lacked the dramatic power required and so cast Mercedes McCambridge, an experienced voice actress and Oscar winner, as the demon's voice. After filming, Warners did not credit her, until Screen Actors Guild arbitration. While that arbitration was concluded quickly enough that McCambridge's name was included in the credits on all but the first 30 prints, it prevented the release of a soundtrack album that was to include excerpts of dialogue. Actress Eileen Dietz, 15 years Blair's senior, stood in for her in the crucifix scene, the fistfight with Father Karras, and others that were too violent or disturbing for Blair to perform. She also appears as the face of Pazuzu. Friedkin gave her no notes, telling her to play the possessed Regan as "a primal force of malevolence ... I wasn't playing a little girl, I was playing the demon that possessed a little girl". Reportedly Warners had forced Friedkin to hire her; he in turn used her only when absolutely necessary. Blair, who recalls Friedkin telling her the film would not succeed if she was not in as many shots as possible, estimates that Dietz's total screen time amounts to 17 seconds. Dietz, angry that her contribution to the film had been minimized, claimed in the media to have done all the possession scenes. Warners ultimately measured her screen presence at 28.25 seconds. Supporting roles The film's supporting roles were cast more quickly. A Philippe Halsman photograph of Pierre Teilhard de Chardin, one of Blatty's inspirations for Father Merrin, inspired Friedkin