Here’s the truth: it’s hard to be scared on a movie set, even a horror movie set. You’re surrounded by crew members. Giant lights illuminate everything around you. Actors in monster make-up sip coffee, practical effects wizards prep blood pumps, and onscreen victims ask the director about their motivation. Everyone knows what they’re doing and what they’re making and they leave the whole "being scared" thing for the audience.

But that’s not always the case. Sometimes, a filmmaker surprises their cast. Sometimes, an actor surprises their director. Sometimes, the creepiness of a scene bleeds out into reality, sending chills down the spines of everyone working on the movie. What should be fake becomes, somehow, powerfully real.

These are the horror movie scenes that actually freaked out the actors who were in them.

The Chestburster in Alien

Alien

There is plenty that director Ridley Scott could replicate in his 1979 horror classic "Alien," like the isolation of deep space or the unsettling biomechanical aesthetics of artist H.R. Giger. But one thing he couldn’t conjure up was authentic fear in his actors. So, for the film’s most shocking scene, in which one of the Nostromo’s crewmembers "births" an alien creature out of his chest at the dining table, he fomented the reaction he wanted by simply not telling his cast what was going to go down.

In the book "Cinema Alchemist," "Alien" art director Roger Christian details how, while the rest of the cast were kept away from the set, Scott had the crew lay actor John Hurt (who plays executive officer Thomas Kane in the film) under a dummy body placed on the table, with only his head and arms exposed. Underneath, the special effects crew worked a blood pump and an alien puppet head. Armed with no other knowledge than a script note that something "emerges" during the scene, Sigourney Weaver, Yaphet Kotto, Veronica Cartwright, Tom Skerritt, Harry Dean Stanton, and Ian Holm react with intense authenticity as a baby Xenomorph tears through Kane’s chest cavity, spurting theatrical blood across Cartwright’s face. Famously, the actor recoiled and passed out from the shock of the gag. She recovered and finished the scene, but she and her fellow actors’ stunned faces will live forever on the big screen as a testament to the power of a well-executed scare. (Anya Stanley)

Bill Hader’s Scenes With Pennywise in IT Chapter Two

Bill Skarsgård terrified audiences everywhere with his new interpretation of Pennywise the Dancing Clown in "It." With a trademark make-up design, sharp teeth, and independently drifting eyes, Skarsgård managed to take the iconic role made famous by Tim Curry and turn it into something all his own. It was on the set of "It Chapter Two," however, that Bill Hader, who played the adult version of Richie Tozier, got a little more than he bargained for during an on-set conversation between scenes with Skarsgård in full Pennywise gear.

The Daily Mail published a series of behind-the-scenes photos showing Hader having a delightful laugh with Skarsgård, only to moments later run away from him in abject terror. As Hader would clarify during an episode of "Conan," his running in fear was genuine, as Skarsgård had revealed that the signature traveling eye of Pennywise was something Skarsgård could do without the assistance of special effects. Hader was so freaked out at the sight of Skarsgård’s independently moving eye that he bolted away and the images of his torment immediately went viral and turned into a popular meme for weeks. Hader admitted during the press circuit that he struggles to "act" scared, frequently smiling or laughing as a defense mechanism, but credits Skarsgård’s genuine ability to scare him for his fearful performance as Richie. (BJ Colangelo)

The Pea Soup Vomit in The Exorcist

The Exorcist

In this 1973 classic, there isn’t much that doesn’t disturb or disgust, and actor Jason Miller really discovered that first-hand on set. The "Exorcist" star — who plays Father Karras, a young priest who agrees to help a young girl who appears to be possessed by a demonic entity — was taken by surprise during one of the movie’s most harrowing scenes.

It’s an iconic moment when Linda Blair’s Regan projectile vomits on Karras, who is attempting to perform an exorcism on the young girl. They used a plastic tube inconspicuously attached to the girl’s chin for the vomit (which was made of pea soup), but it actually misfired. The accident led the mixture to hit Miller right in the face and mouth — and he was genuinely disgusted by the mess-up. He was really coughing and wiping the vomit off of himself in the aftermath — thus, they only needed one take to get the shot. (Lex Briscuso)

The ‘Real’ Phone Calls in Scream

Scream Drew Barrymore

"Scream" has only become more beloved in the years since Wes Craven’s meta slasher flick was released in 1996, reinvigorating the genre for a new generation. One of the most famous elements of the film is the phone calls made by Ghostface to his victims, which we get a taste of early on when Drew Barrymore’s Casey Becker meets her demise surprisingly early in the film. As it turns out, Roger Jackson’s performance as the voice of the killer managed to genuinely scare the actors during production.

In an oral history compiled by The Hollywood Reporter, producer Marianne Maddalena explained that they hid Jackson and actually did the calls on set. "We had separate rooms. He was never around. He was never at craft services. He was absolutely incognito. It made it scary for the actors and Wes just got better performances out of them," Maddalena explained. "It’s a completely different thing than a script supervisor reading the lines. He has an amazing voice, but I don’t know how menacing he would be in person, you know?" In the end, it paid off, as it is one of the most successful horror franchises in history, with a new "Scream" set to hit theaters in 2022. (Ryan Scott)

The Pool Sequence in Poltergeist

Poltergeist

Some urban legends are true. So, yep: the skeletons in the pool in "Poltergeist" were, indeed, real skeletons. The scene in question arrives near the end, finding JoBeth Williams’ matriarch Diane frantic as her suburban home descends into spooky chaos, complete with coffins bursting up through the ground. At one point, Diane stumbles into the yard as rain pours. It’s muddy out there and she slips and falls right into the mucky water of the family’s unfinished swimming pool. At which point screaming skeletons start surfacing.

Williams was terrified to film the scene — but not because of the skeletons. The actress didn’t actually know she was working with real skeletons until after the film wrapped. What scared Williams was the potential for electrical shock with all the production’s live wires about the soaking wet area. To settle her fears, producer (and rumored secret director) Steven Spielberg jumped into the pool with Williams, telling her: "Now if a light falls in, we’ll both fry!" (Chris Evangelista)

A Very Real Lawnmower in Maximum Overdrive

Maximum Overdrive

If a sentient pile of cocaine was allowed to direct a movie, the result would probably look a lot like "Maximum Overdrive." The sole directorial effort from legendary horror writer Stephen King, the film concerns an apocalyptic scenario where every machine on the planet turns against its human masters: trucks, ATMs, arcade cabinets, and even vending machines become violent and start to brutally dispatch every person in sight. One scene in particular is not only an example of a scene that terrified those involved, but stands as a reminder why safety regulations exist on movie sets.

For a scene where a killer lawnmower chases a child through a neighborhood, King insisted that the crew not remove the mower’s blade, even though it could not be seen in the shot. So yes, that child actor is running from a very real, very operational, very deadly lawnmower being driven via remote control. Sadly, this mower would hit a block of wood and send shards directly at cinematographer Armando Nannuzzi, who would lose his eye … and sue King and the film’s producers. Now that’s scary. King would famously sober up in the late ’80s, but "Maximum Overdrive" remains an unfortunate tribute to realism over safety. (Jacob Hall)

Chestburser 2.0 in Prometheus

Prometheus

The 2012 "Alien" franchise follow-up "Prometheus" was a soft reboot in many ways, including when it came to the film’s most gruesome scenes. We all remember the original chestburster, and "Prometheus" star Noomi Rapace was thrust into the sequel’s version. The scene — which features her giving herself abdominal surgery in a medical pod to release an unwanted entity from inside her — profoundly affected her.

"I spoke to [director] Ridley [Scott] about it and said that I would love to find a way to do it as real as possible — to not do it in CGI or to not cut up the scene into small pieces," the actress told Wired in 2012. "We worked for four days on the scene and it messed me up completely."

The preparation and filming for the scene left her really rattled in her home life. "I had two dreams that I remember today," she explained. "I woke up and I went into the loo, saw myself in the mirror, and I realized I had some kind of black veins that began to spread over my whole body. I started to wash my hands and thought the water was going to stop it somehow."

Rapace’s second dream involved her touching her stomach while a mysterious creature moved around inside. She added, "I was so terrified that I was crying, and I woke up and I was crying for real." (Lex Briscuso)

Janet Leigh’s Ongoing Fear of Showers After Psycho

Psycho

Alfred Hitchcock’s "Psycho" is one of those films that truly changed cinema forever. Not only did it solidify the legendary status of then-established actress Janet Leigh, it did the unthinkable — it killed her in the first 47 minutes.

At the time, it genuinely was unthinkable to kill off one of your most famous performers so quickly. It was upsetting to the audience because it meant all bets were off. This established an unshakable sense of dread that no one would forget, and future generations would attempt to replicate (see Drew Barrymore in "Scream"). But what was more shocking than the decision to slay Janet Leigh so quickly was the lasting impact that scene had on her psyche and, as a result, her bathing habits.

After watching herself get murdered in the shower, she seldom took one again unless absolutely necessary. In an interview with the New York Times in 1996, 35 years after the original release of "Psycho," she admitted, "I stopped taking showers and I take baths, only baths." That is, unless she’s staying somewhere that only has a shower, like a friend’s place or a hotel. So how does she get around it in that case? "I make sure the doors and windows of the house are locked, and I leave the bathroom door open and shower curtain open. I’m always facing the door, watching, no matter where the shower head [sic] is." (Ariel Fisher)

Jodie Foster vs Hannibal Lecter in Silence of the Lambs

Silence of the Lambs

Anthony Hopkins’ performance as Hannibal "The Cannibal" Lecter in Jonathan Demme’s "The Silence of the Lambs" is one of the most chilling portrayals of a serial killer ever committed to film — and actually being in the same room as him was even scarier.

Hopkins’ co-star, Jodie Foster, told Vanity Fair that she didn’t get a proper meet-and-greet with him before the production began, and she was "just petrified" during their first reading together. Hopkins had to be locked in behind the glass wall of Hannibal Lecter’s cell at the start of filming each of their scenes, creating a physical barrier between the actors that was reinforced by how little time they spent together off-set. Foster was so scared of Hopkins that she completely avoided him except when they had to be in the same room to film their scenes. It wasn’t until the last day of filming that Foster finally admitted to her co-star, "I was really scared of you!" — to which Hopkins replied, "I was scared of you!" (Hannah Shaw-Williams)

Dracula Scares a Child Actor in The Monster Squad

Monster Squad

At only five years old, Ashley Bank solidified her spot in the horror girl hall of fame when she played the youngest, and only female member of "The Monster Squad" as Phoebe Crenshaw.

Bank hadn’t yet understood that monsters were meant to be scary and has spoken in interviews and commentary tracks about how she was able to handle being around Stan Winston’s creations, like Tom Noonan as Frankenstein’s monster, without being scared. She also found great joy in seeing the Wolfman in only half of his costume and the Mummy walking around without their headpiece. However, it was Duncan Regehr’s performance as Count Dracula that genuinely scared the five-year-old Bank.

When Phoebe faces off with Dracula and he hisses in her face, shouting "Give me the amulet, you b****!" at the small girl, Phoebe lets out a blood-curdling scream before Frankenstein steps in to save his new best friend. Bank’s reaction is one of the best moments of the film, but it was also one of sincere terror as Bank had yet to see Dracula with his red contacts and sharp fangs in. Her scream was her genuine reaction to seeing him in his most monstrous form and having him hiss in her face. Fortunately, though, Bank was not traumatized by the experience, and happily shared the story on the commentary track for "The Monster Squad." (BJ Colangelo)

Gene Wilder Goes Full Crazy-town in Willy Wonka and the Chocolate Factory

Willy Wonka and the Chocolate Factory

If you flipped on "Willy Wonka and the Chocolate Factory" at the right moment, you’d be mistaken for some psychedelic ’70s experimental horror. We all know the nightmarish scene in question — Wonka’s paddle steamer floats down the chocolate river and into a tunnel where golden-ticket holders experience their first acid freakout. Pitch darkness breaks as randomized colors start flashing, subliminal video clips project anything from insects crawling over faces to beheaded chickens, and Gene Wilder’s deranged performance as Wonka goes from eerie singing to enthusiastic screaming directly at his passengers.

Thanks to director Mel Stuart, you can see the abject terror plastered on the faces of children and adults alike in the scene. He didn’t tell any of the performers how Wilder would behave in character for that particular sequence, which led some of the younger actors, like Denise Nickerson (aka Violet Beauregarde), to believe Wilder was suffering a very sincere, very alarming psychotic breakdown. All that confusion, anxiousness, and full-blown terror is genuine — we love traumatizing our nations’ youth, don’t we? (Matt Donato)

Literally Every Moment of The Blair Witch Project

The Blair Witch Project

"The Blair Witch Project" worked so well because it felt so real — not just to the audience, but to the cast, too. Heather Donahue, Michael C. Williams, and Joshua Leonard were tasked with wandering through the woods and capturing their own footage to create the faux documentary, all while directors Daniel Myrick and Eduardo Sánchez followed at a distance. When the three actors weren’t watching, the directors would sneak into their campsite to leave spooky rocks and twigs. Or, even scarier, rattle their tent at night. There was no script, just a general outline, leaving the cast at the mercy of the elements (and the filmmakers). In a sense, it was almost like the filmmakers were hunting the cast members through the woods, just like the Blair Witch herself. (Chris Evangelista)