Horror movies are sometimes hard to watch, leaving us wondering if the actors were scared during filming.

Sometimes the movies are based on true stories, but it's even scarier when the movie set becomes its own supernatural true story.

Here are some of the wildest haunted movie sets.

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Poltergeist Trilogy

Poltergeist

The set of the three "Poltergeist" movies is said to have been cursed with many of its stars dying. (Metro-Goldwyn-Mayer/Getty Images)

The set of "Poltergeist" is said to have been haunted and to have cursed many of the cast and crew. Much like in the film, the actors and crew members experienced a number of strange events on set, which did not stop once filming ended, as tragedy continued to visit cast members.

While filming the first movie, one of the young stars almost choked to death while filming a scene in which his character is choked by a possessed clown doll. In a freak accident, the mechanical clown gripped the boy's neck so tight, he started to yell that he couldn't breathe, and his face turned blue. Steven Spielberg had to jump in and pry the clown's hands off his neck and save his life.

Bad luck followed off the set too, with the deaths of several of the film's stars. 

According to Biography, 22-year-old Dominique Dunne, who played the oldest daughter in the film, was murdered by her ex-boyfriend when she shot down his attempts to win her back. 

Six years after the first "Poltergeist" movie, and one year before the release of the third movie, actress Heather O'Rourke died at the age of 12 after being misdiagnosed with Crohn's Disease in 1987. A year after being misdiagnosed, she became sick again, and after being diagnosed with the flu, she collapsed due to cardiac arrest. While in surgery later that day, she died and was believed to have suffered from a congenital intestinal abnormality.

Another cast member nearly died in a plane crash in 1992, which, according to Popsugar, resulted in the deaths of 27 of the 51 people on board. Three more cast deaths push the narrative that the movie was cursed. Julian Beck from the second film died from stomach cancer in 1985 before the movie was even released, Will Sampson, who played a shaman, died in 1987 while in surgery and the actor who played Pugsley in the original movie was murdered in 2009.

There is an iconic scene in the first movie in which the characters have to swim through a pool of mud and skeletons. According to Biography, JoBeth Williams, who played the mother in the film, claimed that scene was filmed using real skeletons, not props, which led Sampson to perform an exorcism when filming the second movie.

"The Exorcist"

The exorcist

American actress Linda Blair on the set of The Exorcist, based on the novel by William Peter Blatty and directed by William Friedkin. (Warner Bros. Pictures/Sunset Boulevard/Corbis via Getty Images)

"The Exorcist" is often referred to as one of the scariest movies ever made, and it seems the process of making the movie was just as scary. According to The Sun, it all started when William Peter Blatty was writing the book the movie is based on, and his wife started to see her hairbrush floating in the air, and the phone in his house began levitating. 

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There were two very strange disasters that took place on set. In one case, the set of the MacNeil family home inexplicably caught fire and burned down, setting production on the film back six weeks. The only part of the set unharmed was Reagan's bedroom, which is where the demon spent most of its time in the movie.

At another point, the cast and crew arrived on set one morning to find everything covered in snow. According to reports, the explanation was many air conditioners left running combined with the natural humidity on set allowed for snow to form indoors. However, many still find it strange that it snowed indoors.

The set was also plagued by injuries. In one instance, star Linda Blair fractured her back while filming a scene in which Reagan is thrashing around on a moving bed. She revealed this in an episode of "Cursed Sets," saying, "I'm crying, I'm screaming, they think I'm acting up a storm. It fractured my lower spine. No, they didn't send me to the doctor, it is the footage that's in the movie."

Actress Ellen Burstyn also suffered a back injury while filming a scene during which her character is thrown across the room by Blair's character. While filming the stunt, something went wrong with Burstyn's harness, which messed with the timing of the stunt. This caused her to land on her coccyx, permanently injuring her spine.

"The Conjuring"

Lorraine and Ed Warren

Vera Farmiga experienced many unsettling moments while making "The Conjuring." (Getty Images)

The fact that "The Conjuring" is reportedly based on the true story of the Perron family and what they experienced when they moved into a haunted farmhouse, the stories of what occurred on set of the film are unsettling. Both "The Conjuring" and its sequel, "The Conjuring 2," had some disturbing occurrences.

According to Slash Film, one of the film's stars, Vera Farmiga, who played the real-life Lorraine Warren, had a number of strange experiences while making the movie, including waking up throughout the duration of filming between the hours of three and four in the morning, commonly referred to as "the witching hour," when spirits are said to be most active. Farmiga also claims to have found claw marks on her thigh.

Prior to accepting the role, Farmiga found claw marks on her laptop screen shortly after researching the woman she would be playing, Cinema Blend reported. Younger actress Joey King would also wake up with mysterious bruises on her body even though she had no stunts in the film, according to The Independent.

"It wasn’t incredibly painful. It might have felt like a bruise. … It was these three, very distinct, what looks like claw marks, that long nails or long fingertips, like thin fingertips could make," Farmiga told Cinema Blend in 2016. 

"Ghost"

Ghost

The set of "Ghost" is said to have been haunted by the ghost of "Poltergeist" actress Heather O'Rourke. (CBS via Getty Images)

While "Ghost" isn't the first film that comes to mind when most people think of scary movies, the set of the film has a strange connection to another film on this list, which made for some pretty scary moments for the actors while making the movie.

The movie centers on a man coming back into the life of his lover as a ghost after he was murdered, and it is believed that the ghost of Heather O'Rourke haunted that set because it was the same set on which the popular sitcom "Happy Days" was filmed. And O'Rourke appeared on the show occasionally.

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The cast and crew of "Ghost" reported hearing footsteps on the rafters and the sound of children's laughter. As reported by Screen Rant, it was commonly known that O'Rourke enjoyed playing in the rafters, further strengthening the theory her ghost haunted the soundstage.

"The Omen"

The Omen

The set of "The Omen" is thought to be haunted. (FilmPublicityArchive/United Archives via Getty Images)

There were many moments while "The Omen" was filming that suggest the set was haunted. According to Slash Film, even before the movie was made, executive Bob Munger warned producers that making the movie was a bad idea. 

"If the devil's greatest single weapon is to be invisible, and you're going to do something which is going to take away his invisibility to millions of people, he's not going to want that to happen," he reportedly said.

According to Slash Film, the day after filming a scene at a zoo, the man who trained the baboons was mauled to death by a tiger. On a separate occasion, rottweilers on set attacked multiple people, causing injuries.

The film's star, Gregory Peck, evaded death twice during the filming of the movie, both times involving a plane. On one occasion, the plane Peck was flying in was struck by lightning, which could have ended badly but resulted in no issues. Prior to this incident, Peck was supposed to be traveling on a plane that ended up crashing, but he decided to cancel his flight that day.  

There was also an instance in the 2006 remake of the movie in which 13,500 feet of film was destroyed, a portion of which contained the scene where the Damien character's 666 birthmark is revealed.

"Annabelle Comes Home"

Annabelle

Mckenna Grace experienced a few unsettling moments while filming "Annabelle Comes Home." (Rich Fury/FilmMagic)

Actress Mckenna Grace experienced many disturbing moments while filming the sequel to "Annabelle," called "Annabelle Comes Home." In a 2019 interview with The Wrap, Grace went through all the unsettling things that happened to her, ranging from nosebleeds to props mysteriously moving around to random cuts on her face.

Much like Farmiga and King, who woke up with bruising on their bodies while filming "The Conjuring," Grace woke up with "a small cut near (her) hairline on (her) forehead … in the shape of a triangle." She was terrified because the director of the movie told her it meant she was going to be abducted by aliens.

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She detailed another instance when the cast got together for the very first time and the studio lights went out, leaving them in the dark.

"When all of us were on set together for the first time, the lights went out, and we were all freaking out and asking, ‘Annabelle, are you there?’ Then, the lights turned back on, and my nose was bleeding so heavily," she told The Wrap. "It happens sometimes because of allergies but not this heavy. As soon as I left set to get a tissue, it stopped."

Grace also described moments in which the cross hanging off her rosary broke off and fell to the floor, a visiting journalist's watch "went haywire," she saw a shadowy figure sleeping in an empty room on set, the lights in her trailer didn't work and pictures she took of the Annabelle doll came out all black. But the scariest moment during filming came when the Annabelle doll appeared behind a door and then disappeared moments later.

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"Madison and I had a scene where we had to walk down a corridor, and we heard three knocks on a door, but the camera was rolling, so we kept going," she said. "We did it a third time, and we heard it again. At that point, I asked Madison if she heard it, and we both thought it was weird. 

"In the first ‘Conjuring,’ three knocks is a sign of the holy trinity: the Father, the Son and the Holy Spirit. We opened the door, and Annabelle was sitting there in a rocking chair. We thought the guys were just messing with us. The next take, we heard the knock again, and we opened the door again — and Annabelle was gone."