Within minutes of appearing online, it was already a viral hit. At first, the trailer for Cowboys & Aliens seemed to display all the hallmarks of a classic Western: a grizzled, hat-wearing anti-hero, a tense encounter in a saloon and even a poster bearing the words "Wanted: Dead or Alive". But within seconds, the Wild West had suddenly become War of the Worlds and the film's provocatively succinct title was burnt into the viewer's memory.
Although few things are sacred in Hollywood, seeing American cinema's most enduring genre spliced with alien DNA must have been upsetting to some. And even those who were won over by the promo had to wonder how such a concept ever managed to be given the go-ahead, let alone attract two of Hollywood's biggest names - Daniel Craig and Harrison Ford. But although little green men might seem like unusual screen companions for gunslingers, stranger things have happened. In fact, cowboys have squared-off against demons, vampires, robots and even dinosaurs with surprising regularity. Welcome to the world of Weird Westerns.
"Going back to the 1930s, there was an all-midget Western musical - it was called The Terror of Tiny Town," says Paul Simpson, the author of The Rough Guide to Westerns. "Hollywood was making cowboy films in industrial quantities and they were desperate for novelty and I think they took some ideas from the pulp fiction books of the time."
Fast forward to the 1960s and the popularity of the Western had begun to slide. The B-movie director William Beaudine - known in the industry as 'One Shot' because of his aversion to shooting more than a single take of any scene - opted to revitalise the Old West by adding a touch of horror. His gifts to the genre, Jesse James Meets Frankenstein's Daughter and Billy The Kid vs Dracula, are both considered as being among the worst Westerns ever made.
"As soon as you heard the title, you knew there was a compelling proposition there - even if it was going to be very awful when you actually saw it," says Simpson. "It was a kind of marketing ploy to distinguish what would have been fairly routine B-Westerns from the crowd."
Three years later came the arrival of one of the most famous Weird Westerns: The Valley of the Gwangi. The story sees cowboys travel to the Forbidden Valley where dinosaurs still roam, in the hope of catching a Tyrannosaurus Rex to sell to a Mexican circus. With special effects by the revered Clash of the Titans' animator Ray Harryhausen, the film overcame its ridiculous premise to become a cult favourite.
But while some filmmakers were busy exploiting the genre to make a quick buck, others were subverting it to make art. Their works included the notorious acid Western El Topo (The Mole) from 1970, directed by and starring Chilean filmmaker Alejandro Jodorowsky. The mind-bending story, which follows a lone gunman riding through Mexico with only a naked child as his ally, was adored by John Lennon and Yoko Ono, who convinced The Beatles manager Allen Klein to buy and release it internationally.
"The audience probably had to be on the same substances as the cast and crew to have any hope of understanding the film," says Simpson. "People have been trying to decipher Jodorowski's film for years. It's a compelling, if very weird, experience."
In the 1970s, just as the Western as a mainstream Hollywood genre began to disappear into the sunset, Weird Westerns entered their most fruitful decade. In 1973 came the gold standard for the subgenre - High Plains Drifter. The dark, supernatural-tinged story sees Clint Eastwood's "Stranger" entering the fictitious town of Lago to take on rogue gunfighters, as well as eerie scenes in which the town is literally painted red. Also that year came Westworld (probably the only sci-fi Western worth its salt to date), about an amusement park where the robotic mannequins in a Wild West simulation become a little too real.
The two decades that preceded Cowboys & Aliens' release saw just two high-profile Weird Westerns from major Hollywood studios: 1999's Wild Wild West and 2010's Jonah Hex. While the former turned a respectable profit at the box office (and the latter bombed atrociously), both were savaged by critics. Will Smith, the star of Wild Wild West, even felt the need to apologise for his movie, which featured a 50-storey-tall mechanical spider.
"The problem was that neither was particularly well-made and sometimes the risk with trying to please both sci-fi and Western fans is that you end up satisfying neither," says Simpson.
Valley of the Gwangi 1969
Originally conceived as a follow-up to King Kong, the script for this cowboys-meets-dinosaurs caper sat on a shelf for almost 30 years before finally going into production. The involvement of Harryhausen ensured that a film that might otherwise have been forgotten still has an army of adoring fans even today. It even featured briefly in an episode of the sitcom Friends - being enjoyed by palaeontologist Ross.
El Topo 1970
Filled with violence and disturbing imagery, Alejandro Jodorowsky's surreal art Western is an uncomfortable watch. With washed-out landscapes, bizarre characters and spiritual conundrums, you'll never see another film like it. As well as Lennon and Ono, its famous fans have included David Lynch, Dennis Hopper, Bob Dylan and Marilyn Manson. Despite this, it was a legendary "lost film" for some 30 years, until it finally received a DVD release in 2007.
High Plains Drifter 1973
The director and star Clint Eastwood wanted High Plains Drifter to offer the same gritty, revisionist take on the Old West that Sergio Leone had pioneered with A Fistful of Dollars, while also adding a subtle, supernatural element that was altogether new. The star of an earlier generation of Westerns, John Wayne, wrote to Eastwood saying he hated the film's violence, and arguing that as portrayed the townsfolk "did not represent the true spirit of the American pioneer" when defending themselves against marauding bandits.
Westworld 1973
The author Michael Crichton dreamt up Westworld after a trip to Disneyland, where he had been impressed by the animatronic mannequins on show. He decided to write a screenplay about a Wild West-themed amusement park where the robotic extras (including The Gunslinger character, played by Yul Brynner) break their programming and become dangerous. Crichton revisited the idea of an amusement park becoming overrun by its own specimens in his most famous novel, Jurassic Park.
Near Dark 1987
The recent Oscar winner Kathryn Bigelow wanted her directing debut to be a straight Western, but because the genre had been out of fashion for almost two decades it was decided that vampires should be added. Despite featuring bloodsuckers and a contemporary setting, the Arizona backdrop gives the tale of nomadic vampires an authentic Wild West feel. The film shared three cast members (Bill Paxton, Lance Henriksen and Jenette Goldstein) with 1986's Aliens, directed by Bigelow's then husband James Cameron.