Working on a horror movie set can be stressful for a lot of reasons.

Intense scheduling may make the crew exhausted. Practical effects might result in actors becoming sick or getting injured. Not to mention, terrifying on-set ambiance has the capacity to leave everyone involved with nightmares.

Generally speaking, all of this will be chalked up to the expected hazards of working in horror. But, in the cases of some unluckier projects, the day-to-day risks can turn from the mundane to the otherworldly.

For decades, various scary movie staffs have alleged paranormal activity—and even a few ghost sightings—during production.

From mysterious claw markings to multiple homicides, here are the harrowing experiences of six horror film crews.

Note: Debunked claims (like those surrounding the Poltergeisttrilogy) and on-set accidents (like the tragic helicopter crash of the Twilight Zonemovie) have not been included.

1. Mysterious claw marks and falling lights on the set of Annabelle

Two major paranormal events hit the set of Annabelle.

First, during pre-production, director John R. Leonetti reported seeing and taking a picture of "three fingers drawn through the dust along the window... backlit by the moon." (Notably, the demon of Annabellehas three fingers/talons.) Naturally, it spooked the director.

Second, producer Peter Safran can attest that, while mysterious markings may be easy to dismiss, sudden, unexplainable events—that mirror the horror of the film being made—are harder to write off. He recounted the following to The Hollywood Reporter:

"We shot in this amazing, old apartment building near Koreatown and we had some funky stuff go down... In particular, the first day that the demon was shooting in full makeup, we brought the demon up in the elevator. He walks out and walks around to the green room to where we’re holding the talent, and just as he walks under—a giant glass light fixture is being followed by the actor playing the handyman of the building—and all of a sudden the entire glass light fixture falls down on his head, the janitor‘s head. And in the script the demon kills the janitor in that hallway. It was totally freaky."

Annabelleis available to rent or purchase with Prime Video.

2. A very selective fire on the set of The Exorcist

The Exorcist was notoriously wrought with challenges before, during, and after its release. (Fainting audience members, public denouncements by clergy, serious cast member injuries and reports of stalking are just a few of the horrors that plagued the production.)

But, only one incident rises to the level of truly otherworldly. During a celebratory 45th anniversary Q&A with star Ellen Burstyn, director William Friedkin recounted a fire that burned a large portion of the set of The Exorcistto the ground.

Two sets had been created on one sound stage—the main MacNeil house and Regan's bedroom. (If you haven't seen it, Regan is the young girl who, when possessed by a demon, famously projectile vomited green goo into cinematic history.)

The serious fire, believed to have been caused by a pigeon flying into a light box, destroyed the MacNeil home and put the production on hiatus for six weeks. However, despite the fire's severity, it somehow managed to leave the nearby set of Regan's bedroom entirely unharmed.

Friedkin believes this event to be the only part of his Exorcistexperience related to "some kind of bad karma."

The Exorcistis available to rent or purchase with Prime Video.

3. Inexplicably destroyed footage of The Omen

Technically speaking, this paranormal activity occurred in the editing room (not on the set) of The Omen—but its effects on production were just as massive.

After spending an entire day of shooting the infamous birthmark scene for the 2006 remake, director John Moore claims nearly all of the resulting footage was inexplicably lost. An accident in the processing lab destroyed 13,500 feet of film, an unheard of loss on most film sets that Moore says had the baffled lab technicians "in tears."

The scene, which reveals a young boy to be the antichrist, had to be entirely reshot.

Add this bizarre erasure to the original Omen's reports of not one, but two freak lightning strikes, as well as a number of unusual deaths close to the production staff, and you've got a pretty decent case for a curse.

The Omenis available to stream on HBO Go.

4. Two strangers on the set of The Nun

Seems like you can't make a movie about Ed and Loraine Warren, IRL paranormal investigators, without getting a big serving of spooks during filming.

The Conjuring Universe is both a major asset and liability for Warner Brothers. On the one hand, the still growing franchise's five films have already grossed over a billion and a half dollars. On the other hand, the people who make these movies seem to inevitably face terrifyingstuff.

From unexplained bruising to an alleged water poltergeist, the CU has seen it all. But one story from the series' most recent installment, The Nun, is of particular note. Director Corin Hardy claims to have seen not one, but two apparitions.

While filming a sequence in the narrow hallway of a real-life Romanian castle, Corin recounts stepping into a side room to allow a camera to pass. When he entered the dark space, he saw two men sitting at the back of the room. He assumed they were crew members.

Corin stayed in the room for one take and, upon completion, turned to speak with the men. But they were gone.

In a room with only one way in and one way out, Corin was understandably terrified.

The Conjuringis available to stream on Netflix.

5. The horrifying deaths surrounding Rosemary's Baby

This Mia Farrow-starring classic undoubtedly champions the most terrifying occurrences of any film on this list—and may even take the cake for most misfortunate movie in history.

Numerous tragic deaths, including the murder of director Roman Polanski's wife, Sharon Tate, by members of the Manson family, plagued the film's cast and crew following its successful release.

One near death, however, may most closely tie these horrendous events to some kind of curse. Less than a year after the premiere of Rosemary's Baby,producer William Castle was hospitalized with severe kidney stones. As a result, Castle experienced hallucinations of scenes from the film and was said to have at one point screamed, "Rosemary, for God's sake, drop the knife!"

One could easily argue that it would make sense for a producer's subconscious to bring up his jarring, recent work in a moment of distress. But something about this particular utterance screams paranormal possession.

Castle survived the ordeal, but, as Vanity Fairpoints out, he was never again part of a major hit.

Rosemary's Babyis available to stream on STARZ.

6. The ghost of 1990's rock on the set of The Exorcism of Emily Rose

The Exorcism of Emily Roseisn't the greatest possession story ever told—it currently holds a 44% on Rotten Tomatoes—but, it may take home the trophy for funniest IRL haunting.

Star Jennifer Carpenter didn't report a lot of abnormal activity on set, but she did have a spooky and recurring issue at home while on the project.

"Two or three times when I was going to sleep my radio came on by itself," Carpenter told Dread Central. "The only time it scared me was once because it was really loud and it was Pearl Jam’s 'Alive.'"

Love a ghost with taste.

The Exorcism of Emily Roseis available to rent or purchase with Prime Video.