1. The movie is based on a book, which was inspired by a real-life exorcism. The novel, also titled The Exorcist, written by William Peter Blatty, was first published in 1971. It was based on the 1949 Maryland case of a 13-year-old boy, only known under the pseudonym of Roland Roe. The boy was suffering from an inexplicable ailment after the death of an aunt who had introduced him to the Ouija board and started presenting extreme signs of demonic possession. The first attempt at the ritual was performed by Roman Catholic priest, Edward Hughes, at Georgetown University Hospital (a Jesuit institution). The exorcism was unsuccessful and stopped when the priest was physically harmed, as the boy was said to have broken free from his restraints and slashed the priest using a mattress spring. Rev. William S. Bowdern, in St. Louis, was granted permission to perform another exorcism by the Catholic church. The boy is said to have undergone around 30 exorcisms, many in which he succeeded in breaking free from his restraints and becoming violent. Roland had no recollection of his possession or exorcism when breaking free and went on to live a normal life.
2. The book on which it is based was initially a failure when published. The author hit some luck when he was invited as a last-minute guest on late night show, The Dick Cavett Show. Subsequently, the book hit The New York Times best-seller list.
3. The author of the book also wrote the screenplay for the film and acted as producer. Previous to making the bestseller list, Hollywood studio after Hollywood studio rejected his screenplay for the film. After his book became a success, Warner Bros bought the rights to the film, and Blatty acted as producer.
4. The demon’s name in the film is Pazuzu. The name of the demon is never explicitly mentioned in the film. At the beginning of the film when Father Merrin stands in front of a statue in an archaeological site in Iraq, he is actually in the ancient Nineveh. The statue is that of Pazuzu. He is an ancient Assyrian and Babylonian demon, king of the demon winds and son of the Hanbi, the god of evil. He had the power to control winds that could cause destruction and famine. Though Pazuzu was an evil force and was to ascend the underworld throne, he actually protected pregnant women by keeping the demon goddess Lamashtu at bay, who was said to harm pregnant women and babies.
5. The Macneil house caught fire during the shoot, except Regan’s room. A very mysterious fire left the WHOLE set damaged, but Regan’s room was completely unharmed.
6. The iconic eerie scene of the priest’s arrival, as he steps out of a cab and in front of the Macneil home, is actually inspired by a series of three oil paintings. Director William Friedkin took inspiration in The Empire of Light, painted by surreal artist René Magritte.
7. A real-life suspected serial killer makes an appearance in the film. Paul Bateson, a real-life X-ray technician, played the role of the radiologist’s assistant in the scene where Regan is having a carotid angiography. He was arrested for homicide in 1979, after meeting film critic Addison Verrill, having sex with him, and proceeding to bash his skull in with a skillet. Bateson boasted about killing other men while awaiting trial, claiming that he did it for fun and dumped their bodies in the Hudson River. Authorities suspected him of being a serial killer that had been targeting gay men in the years of 1977 and 1978, and wrapping their chopped up remains in plastic bags. These were known as the Bag Murders. Though they had a confession, they couldn’t link any evidence to his claim. Sentenced to 20 years for the murder of Addison Verrill, Bateson became a free man in 2004.
8. Linda Blair secured the role of Regan Macneil, having defeated 500 other actresses. WOW! There was actually a point during the search for the right child actress, in which the director considered auditioning adult dwarfs, as it was proving to be a challenge.
9. Willy Wonka’s Violet, actress Denise Nickerson, almost played Regan, before being pulled by her parents because they found the script so disturbing.
10. The role of Chris Macneil, played by Ellen Burstyn, was originally turned down by both, Jane Fonda and Audrey Hepburn.
11. The role of Father Dyer is played by real-life priest William O’Malley. He also served as technical advisor to the film.
12. Director William Friedkin actually took deliberate measures to abuse the cast for a fear effect. He went as far as firing guns without warning behind the actors to frighten them. He slapped Father O’Malley across the face to catch footage of his shocked reaction for the film. He also put Ellen Burstyn and Linda Blair in harnesses and had them shook and yanked violently.
13. The screams you hear when Regan’s mother is thrown to the floor after the possessed girl slaps her, are actually genuine. She permanently injured her spine during the shooting of this scene because she was pulled too hard by a cable.
14. Linda Blair also injured her back while filming. A piece of rigging broke while shooting one of the infamous possession scenes.
15. Regan’s room was literally freezing. The director wanted it to appear genuine that the room was cold and literally chilled it to achieve this effect. The entire room of Regan was refrigerated to catch the breath of the actors on camera. The room was actually 30-40 degrees below freezing.
16. Mercedes McCambridge went to extreme lengths for the voice of the demon. She provided the vocalizations of the demon and in order to perfect the distorted voice, she actually gave up sobriety. She chain-smoked cigarettes, drank heavily, even ate raw eggs to master the Satanic voice. She was also physically bound to a chair with torn sheets by arms, legs, ankles and writs to achieve a more realistic sound.
17. Jason Miller, who played Father Karras, had actually studied to become a priest before dropping out because a loss of faith.
18. Stanley Kubrick turned down directing the film.
19. Max von Sydow, who played elderly Father Lankester Merrin, was only 43 years old. He actually had to undergo 5 hours of makeup every day before shooting.
20. Actress Mercedes McCambridge ended up suing Warner Bros because they failed to credit her for the voice of the demon.
21. Linda Blair’s double, Eileen Dietz, also sued for not being credited for the vomiting sequences. The shooting of these were actually so complex that Dietz couldn’t even close her mouth. There was an actual “vomiting apparatus” involved.
22. During the first day of filming, Max von Sydow (Father Merrin) actually forgot his lines because he found Linda Blair’s crude dialogue so unsettling.
23. Linda Blair received an insane amount of death threats. The majority of these were from religious zealots, many who believed her to be Satan’s voice and helper. These threats got to be so horrendous that Warner Bros had to hire bodyguards to be with her 24 hours a day, seven days a week, for nearly 6 months. The threats actually didn’t stop after the movie was released or when buzz died down, they continued on for years.
24. Warner Bros originally wanted Marlon Brando for the role of Father Merrin. The director wasn’t keen on the idea because he thought Brando’s involvement with the film would overshadow its importance.
25. Jack Nicholson almost got the role of Father Karras before Jason Miller landed it.
26. People actually believed the film was cursed. The popular belief was that even playing the film could invite demonic possession. Televangelist Billy Graham said, “There is a power of evil in the film, in the fabric of the film itself.”
27. The film was banned in the UK. The movie was released with an X rating in the UK in 1974. It was later banned by a few local authorities, and in 1988 the sale of the film was banned under The Video Recordings Act. It wasn’t until 1999 that the film was legally released again in the UK.
28. It was banned in every Middle Eastern country except Lebanon. The re-release went on to be banned there too.
29. The sound of the demon leaving Regan’s body is actually recordings of pigs being led to slaughter.
30. The scenes where Father Karras visits his mother in Bellevue actually contain real mental patients and some were recorded using hidden cameras.
31. There was quite a number of deaths surrounding the movie. Actor Jack MacGrowan died from the flu shortly after shooting ended. Actress Vasiliki Maliaros also died during post-production, due to natural causes. Both of their characters died in the film. Linda Blair’s grandfather and Max von Sydow’s brother both died during shooting. The son of Mercedes McCambridge murdered his wife and two daughters before taking his own life in 1987.
32. A woman was so frightened at a showing of the movie that she passed out and broke her jaw. She later sued Warner Bros and ended up settling for an undisclosed amount.
33. The movie made people so nauseous that theatres started handing out bags to vomit in with every movie ticket.
34. The cast and crew believed the set to be actually cursed and a priest had to come bless it.
35. This was the first film to be nominated for Best Picture at the Academy Awards.