From Krampus to Santa Claus, the holiday season is filled with all sorts of memorable characters. On December 26, 1973, the studio executives at Warner Bros. added a new kind of yuletide tot into the mix: Regan MacNeil, a demonic tween famous for her distaste for pea soup and unholy attitude toward religious relics. Here are 20 fascinating facts about William Friedkin's groundbreaking horror film.

1. The Exorcist is based on a true story.

William Peter Blatty’s novel is based on the real-life 1949 exorcism of a young boy, known by the pseudonym Roland Doe. The story became national news, and caught the interest of Blatty, who was a student at Georgetown University at the time (hence the change in location).

2. William Peter Blatty wrote The Exorcist novel in a cabin in California.

In Beyond Comprehension: William Peter Blatty's The Exorcist, one of the featurettes on Warner Bros.'s special 40th edition Blu-ray, Blatty returns to the scene of The Exorcist’s beginning: the cabin in the hills of Encino, California where he wrote the novel more than four decades ago.

3. The name of the demon in The Exorcist is Pazuzu.

Though it’s never stated in the film, the demon that takes possession of Regan MacNeil has a name: Pazuzu, which is taken from the name of the king of the demons in Assyrian and Babylonian mythology.

4. Mercedes McCambridge provided the voice of the demon in The Exorcist.

The woman Orson Welles once dubbed “the world’s greatest living radio actress” was hired to provide the voice for Linda Blair’s most demonic moments, a decision that became the source of much controversy when McCambridge was not credited for her performance. Some say that this decision was solely McCambridge’s, who claimed that she didn’t want to take away from Blair’s performance, then later changed her mind. Under the threat of legal action, her name was quickly added to the credits.

5. Chain smoking and whiskey helped McCambridge achieve Pazuzu's raspiness in The Exorcist.

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Sounding like a demon has its downsides. In the case of McCambridge, she believed that chain smoking and a diet of raw eggs and whiskey were the key to a great vocal performance.

6. Pig squeals were a key part of The Exorcist's sound design.

Much of Regan’s moaning and grunting were created by remixing pig squeals. When the demon is finally exorcised from her body, the sound you hear is a group of pigs being led to slaughter.

7. The Exorcist was the first horror film to be nominated for a Best Picture Oscar.

The horror genre has never gotten much love from the Academy. Though there still seems to be a bias against scary movies during awards season, The Exorcist earned 10 Oscar nominations in 1974, including a Best Supporting Actress nod for Linda Blair, who was just 15 years old at the time. Unfortunately, the teenager’s nomination was met with much controversy as word about McCambridge’s contribution to the role spread.

8. Violet Beauregarde was considered for the role of Regan in The Exorcist.

Denise Nickerson, who most famously played Violet Beauregarde in Mel Stuart’s Willy Wonka & the Chocolate Factory, was in contention for the role of Regan. But then her parents got a hold of the script and, troubled by what they read, pulled her from the production’s shortlist of young actresses.

9. Linda Blair's mother loved The Exorcist script.

Ironically, Linda Blair’s agents never even considered her for the role, though they did send the producers more than two dozen other young actresses to consider. It was Blair’s mother who brought her to the attention of the studio’s casting department and Friedkin.

10. Blatty insisted that William Friedkin direct The Exorcist.

Blatty made a smart decision when he sold the rights to his novel, but stayed on as one of The Exorcist’s producers. That way, his opinion would have to matter. And while the studio had its own short list of directors to approach for the gig—Arthur Penn, Peter Bogdanovich, Mike Nichols, and Stanley Kubrick among them—Blatty only had eyes for Friedkin, believing that the film would benefit from a grittier style, similar to what Friedkin had done on The French Connection. When the studio told Blatty that they had hired Mark Rydell for the film, Blatty stood his ground—and won!

11. Marlon Brando was the studio's first choice for Father Merrin in The Exorcist.

It was Friedkin who vetoed this decision, believing that any movie starring Marlon Brando would immediately become a “Brando movie,” which would detract from the story at hand. The role eventually went to Max von Sydow.

12. Max von Sydow was only 44 at the time of shooting The Exorcist.

It took many hours in the chair with makeup artist Dick Smith to age the actor the 30 or so years the role required. Some have even joked that there are scenes in which von Sydow is wearing more makeup than the demonic Regan. Von Sydow’s three-hour daily aging process was achieved with a mix of stipple and liquid latex.

13. Jason Miller was a last-minute—albeit intentional—substitution in The Exorcist.

There were a few big names being bandied about for the role of Father Karras, with Jack Nicholson in the early mix before Blatty settled on Stacy Keach. But then Friedkin happened to see a performance of That Championship Season, which was written by and starred Jason Miller. Friedkin knew they had found their man and, as he recounted in his 2013 memoir, The Friedkin Connection (part of which is excerpted in the 40th edition Blu-ray), they purchased Keach out and in stepped Miller, in his feature acting debut.

14. The Exorcist's most famous image is based on a series of René Magritte paintings.

The Exorcist’s most iconic image—the one that would eventually serve as its poster and movie box art—is of the moment that Father Merrin arrives at the MacNeil residence and, illuminated by a street lamp, looks up at the home. This image was inspired by René Magritte’s Empire of Light paintings.

15. "The Exorcist Steps" are still a popular tourist attraction.

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At the end of M Street in Washington, D.C. is where you’ll find one of the film’s location landmarks: a set of stone stairs onto (and down) which Regan “throws” Father Karras from her window. Understandably, they have come to be known as “The Exorcist Steps.” Rumor has it that on the day of filming the scene in which a stuntman rolled down the steps, Georgetown students who lived nearby rented out their rooftops to the tune of $5 per person so that interested onlookers could get a better view.

16. Throwing anyone down The Exorcist stairs from Regan's window would be impossible.

Yes, even for a kid with demonic strength, because, in reality, Regan’s window was located about 40 feet from the top of the stairs. It was a bit of Hollywood magic-making—a.k.a. the addition of a wing built by the production’s set decorators—that made the trajectory of Karras’s untimely tumble seem possible.

17. Many of The Exorcist's cast and crew members believed the set was cursed.

Filming in the U.S. took place in both New York City and Washington, D.C. After a number of eerie incidents on the New York City set, including a studio fire that forced the team to rebuild the sets of the house interiors, Blatty and Friedkin regularly brought in a priest, Father King, to bless the cast, crew, and set when production moved to D.C. By the end of the film’s production, nine people associated with its making had passed away.

18. Regan prefers Andersen's pea soup.

By now it is well known that the substance Regan projectile vomits onto Father Karras in one of the film’s most famous—and disgusting—scenes is pea soup. But more specifically, it’s Andersen’s pea soup, mixed with a little oatmeal. Campbell’s soup was tried, but the crew apparently didn’t like the effect as much.

19. Jason Miller's disgusted reaction to being covered in said pea soup is authentic.

Friedkin was known for sometimes using manipulative tactics in order to elicit the most authentic reactions possible from his actors. Miller was told that the substance would hit him in the chest only; whether that was a lie or the equipment misfired is debated. But Miller’s disgusted reaction is absolutely real. Unsurprisingly, the scene only required one take.

20. The Exorcist made a few audience members nauseous, too.

So many, in fact, that some theaters began handing out The Exorcist barf bags with every ticket.