The Terminator's very unusual origin story in James Cameron's dreams

Forty years ago, a cinema icon walked on screen, ready-made. With Arnold Schwarzenegger's Austrian drawl, some very cool sunglasses, and a massive gun, The Terminator made an instant impact. James Cameron's sci-fi action movie was a box office hit to the tune of $78m (£59m) — 12 times its stated production budget.

But that murderous cyborg from the future came from a bizarre source. The original idea that became The Terminator arrived in James Cameron's mind while he was fast asleep.

In early 1982, Cameron was reeling from the terrible experience of making his debut feature film Piranha II: The Spawning. There are questions to this day about how much creative control Cameron actually had on that movie and, for a long time, the director refused to acknowledge the film as his debut. He completely disowned it.

So it's no surprise that he was having some pretty lurid, stressful dreams around this time. When he fell ill, he had a terrifying dream about a creature with a metal torso crawling towards him out of an explosion, wielding kitchen knives in both of its hands.

Read more: James Cameron finds some of The Terminator 'pretty cringeworthy' (BANG Showbiz)

Cameron was inspired in the wake of this dream by other directors of the era like John Carpenter, who had recently made Halloween. He turned his dream into the script for a slasher movie, while staying at the California home of sci-fi writer Randall Frakes, as Cameron explained in an interview on the original home video release.

"My contemporaries were all doing slasher-horror movies. John Carpenter was the guy I idolised the most. He made Halloween for $30,000 or something. That was everyone’s break-in dream, to do a stylish horror movie. It was a very slasher film type image. And it really was the launching pad for the story."

Cameron, though, added a sci-fi twist to the slasher concept, turning his version of Michael Myers into a cyborg sent back in time to shoot down a human resistance before it even starts. This idea proved to be a terrific addition to the story. Around this time, he also came up with the idea of a cyborg made from liquid metal — an idea that was shelved until Terminator 2 provided the necessary tech advances to make it work.

Read more: Terminator: Dark Fate's Mackenzie Davis says it would be 'insane' to think people wanted a sequel (Yahoo Entertainment)

Once Cameron had a decent script outline, producer Gale Anne Hurd — who had only recently formed Pacific Western Productions after being Roger Corman's assistant — was interested. Cameron signed the rights over to her for just a dollar on the promise that she would only make it if he could direct it. They were able to get distribution via Orion Pictures, who agreed to put the film out there if someone else would finance the production.

In order to get this finance from Hemdale Film Corporation, Cameron had his pal — actor Lance Henriksen — turn up to a meeting dressed as the Terminator. The stunt worked and may well have even paved the way for Cameron's now-famous Aliens stunt pitch a few years later.

The rest is history. Cameron landed upon Schwarzenegger, who had previously been in talks to play Kyle Reese instead. Sylvester Stallone and Mel Gibson both turned down the chance to play the Terminator, while OJ Simpson was even suggested. Even Schwarzenegger wasn't convinced and commented to an interviewer on the set of Conan the Destroyer that Terminator was "some s*** movie" he was making. How wrong he was!

By the spring of 1984, Cameron was on set and preparing to film the movie inspired by a dream he had during one of the lowest points of his life. Even he couldn't have known just how big that dream would end up becoming. It certainly made it easier to forget about the piranhas.

The Terminator is available digitally and is still in some UK cinemas for its 40th anniversary.