Behind the scenes secrets from the original Alien movie

"In space, no one can hear you scream." Eight words that became one of the most memorable movie taglines of all time when they appeared in the marketing for a little film called Alien. Ridley Scott's outer space horror movie became a box office success in 1979 and spawned a franchise that is still going strong today with Alien: Romulus.

But back in the 1970s, this was anything but a sure thing. Nobody knew whether HR Giger's horrific alien creature would hit big with audiences and it's fair to say that very few would have pegged this to become a franchise with a 45-year future.

So with Alien: Romulus splattering the multiplex with gore this week, now is a great time to take a look back at the earliest days of this franchise and lift the lid on some fascinating behind the scenes stories from that first Alien movie. In trivia land, no one can hear you scroll.

They 'stole' the story from lots of other movies

Alien screenwriter Dan O'Bannon was very honest about the influences behind the movie, telling author David McIntee in his book Beautiful Monsters: "I didn't steal Alien from anybody. I stole it from everybody." O'Bannon has cited 1950s sci-fi classics including The Thing From Another World — later remade by John Carpenter as The Thing — and Forbidden Planet, as well as Mario Bava's 1960s horror oddity Planet of the Vampires.

Read more: Alien movies ranked worst to best according to fans (Yahoo Entertainment UK)

At the pitching stage, the movie was described as "Jaws in space" and, when Ridley Scott came aboard, he wanted it to be a space-bound spin on The Texas Chainsaw Massacre, emphasising horror over sci-fi or fantasy. That's an eclectic range of inspirations, which combined to make something utterly unique and individual.

Star Wars got them the green light

20th Century Fox wasn't very keen on putting money into a sci-fi film in the middle of the 1970s. But after George Lucas convinced them to make Star Wars and it became the highest-grossing movie of all time, space became a red-hot commodity in Hollywood.

In the documentary The Beast Within: The Making of Alien, O'Bannon said: "They wanted to follow through on Star Wars, and they wanted to follow through fast, and the only spaceship script they had sitting on their desk was Alien."

While the James Bond franchise groped for Moonraker in an attempt to join the space trend, with disastrous consequences, Fox had Alien ready to go.

Sigourney Weaver was allergic to her sweat

The womb-like environment of the Nostromo spaceship was supposed to be a sweltering place to be, which meant that the actors had to look sweaty at all times. In order to achieve this effect, the actors were smeared with the sweetening substance glycerin.

Read more: Sigourney Weaver paved way for women in horror, says Alien: Romulus star (PA Media)

Unfortunately for Ripley actor Sigourney Weaver, it turned out that she was allergic to the combination of that glycerin and the hair of the four different but identical cats brought to set to portray the crew's pet Jones. Thankfully for all of us, she was able to continue her role, becoming one of horror cinema's greatest heroes.

They used children to make the spaceship bigger

The Nostromo had to look massive in order for the movie to work. Part of the terrifying effect is in the contrast between the enormous spaceship and the claustrophobia the crew feels at being trapped aboard with a deadly alien critter. Scott and cinematographer Derek Vanlint volunteered their young sons to come up with an ingenious solution to this.

Children in small spacesuits were used as stand-ins for the adult actors for certain scenes, enhancing the scale of the sets and the alien. Eventually, oxygen systems had to be worked into these suits because both the young and adult actors found themselves at risk of passing out due to the heat.

LV-426 has rock band lighting

When the crew of the Nostromo lands on the moon LV-426, they discover a chamber full of eggs. This chamber is bathed in unearthly lighting to enhance the sci-fi weirdness of the whole thing. But what's truly bizarre is that part of that lighting is down to The Who.

The rockers' crew was on the sound stage next door to the Alien set and they loaned the production some of the lasers they were testing for one of their upcoming stage shows. So part of the sci-fi glow of LV-426 came courtesy of British rock royalty.

Ridley Scott played the alien egg

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Scott's influence behind the camera is, of course, all over Alien. But he also made a very brief appearance on screen in the movie. During the scene when John Hurt's ill-fated character Kane examines an alien egg, Scott donned a pair of rubber gloves and stuck his hand into the bottom of the fibreglass egg prop to make it look as if something was moving inside.

It's just one of the many brilliant bits of handmade, DIY filmmaking that went into making Alien such a classic. Speaking of which...

Those chestburster reactions are real

One of the most well-known stories from Alien is the fact that most of the cast had no idea what was going to happen in the iconic chest-burster scene. That's a bit of an over-simplification, as they'd previously seen the terrifying alien puppet and knew Hurt's chest was going to explode. However, they weren't prepared for the scale of the gore.

Read more: Alien: Romulus teases gruesome Chestburster scene in final trailer (Digital Spy)

The fake torso used for the scene was rigged with all manner of squibs and apparatus for shooting blood all over the ship. Veronica Cartwright felt a jet of gore fire right at her and her intense, memorable reaction was entirely real, along with that of her co-stars.

It's this realism that has ensured the chest-burster's status as one of the most famous movie sequences of all time. In 2007, a poll by Empire Magazine called it the best 18-rated movie moment of all time and, frankly, it's hard to disagree.

Ripley nearly ended up headless

Without Ripley, it's difficult to imagine Alien ever becoming a franchise. Weaver's performance was integral to the first four Alien movies and her influence can be felt in the protagonists since, played by the likes of Noomi Rapace and Katherine Waterston. But Ridley Scott wanted to kill her off in the final moments of that original movie.

Scott pitched an extra sequence for the end of Alien, which became Ripley's final encounter with the xenomorph on the Nostromo's escape shuttle. He got given extra money to shoot it, but didn't get permission for his ambitious ending. Scott wanted the xenomorph to bite Ripley's head off and then record a log entry using her voice. Chilling, but a risk too far for the producers.

The egg on the poster isn't an Alien egg

The most famous image used in the promotion of Alien wasn't the xenomorph at all, with HR Giger's beastie concealed until the pivotal moment on screen. Instead, it was the simple poster, featuring a glowing alien egg. But that egg isn't actually one of the eggs that you can see in the movie.

Read more: Alien: Romulus review: supercharged spectacular blasts flagging series back to gory, glorious life (Evening Standard)

During test filming, the crew used ordinary chicken eggs as a stand-in for the alien ones they would later build. Those eggs showed up in teaser trailers and so, for marketing continuity, one appeared on the poster as well. So the emblem of the franchise is an egg that never actually appears in the movie.

The xenomorph made it on to a 700-year-old building

In 2013, the internet became aware of a very interesting gargoyle on the walls of Paisley Abbey, just outside Glasgow. Bizarrely, this 13th century church appeared to have a xenomorph staring down from its walls. Sadly though, there was a very reasonable explanation for all of this.

In 1991, 12 of the 13 original gargoyles were rebuilt by stonemasons due to their sorry state and Reverend Alan Birss told BBC News he's pretty sure of what happened. "I think it was a stonemason having a bit of fun," he said. "If he was thinking of an alien, perhaps the alien from the film was his idea of an alien."

That's much less exciting than the idea of a xenomorph reaching back through time and ending up on a medieval Scottish church. Even the mythology of Alien has its limits.

Alien: Romulus is in UK cinemas from 16 August.