July 18, 2011 -- Take a classic Western, throw in an army of scary sci-fi aliens, add some serious star power, and you get... a summer blockbuster? That's what the Hollywood mega-producers Steven Spielberg, Ron Howard, and Brian Grazer behind "Cowboys and Aliens" are hoping for.
The film's title may be a bit of a punch line, but the movie plays the genre mash-up surprisingly straight. Even the film's star, Harrison Ford, was a bit bewildered by the idea at first.
"When I read it, I frankly didn't get it," Ford told "Nightline" anchor Terry Moran.
But his desire to "do the cowboy part" won out over his trepidation.
"I've wanted to do a western for 25 years, they just stopped making them," Ford said. "And it was clear that they'd found a new way to make them from the title."
Watch "Nightline's" Terry Moran's full interview with "Cowboys and Aliens" stars Harrison Ford, Daniel Craig and Olivia Wilde, as well as director Jon Favreau, TONIGHT on "Nightline" at 11:35 p.m. ET
Finding a new way to make a Western was key, according to the film's director, Jon Favreau, since the genre typically has not performed well commercially.
"What the alien thing allowed us to do was create a sub-genre because alien movies tend to do very well worldwide," he said, nodding to the importance of overseas box office revenue.
"We really tried to maintain all the paradigms of the Western whenever we could," Favreau said, "but still give it that summer popcorn feel with a little bit of action, a little bit of fun."
Set in the old American West, "Cowboys and Aliens" stars Hollywood heavyweights Ford, 69, and Daniel Craig, 43, alongside actress Olivia Wilde, 27. Craig's character is an outlaw on the run who joins forces with Ford's cattle baron to face off against a mysterious band of marauding aliens.
Craig said the tone of the story is what sold him on it. "They didn't want to make a gag out of it. Even though the title is a gag, they wanted to sort of play it for real," he told Moran.
And shooting the movie gave its stars a chance to live out their cowboy fantasies. For Englishman Craig, "the chance to actually get on a horse every day and just put the hat on and put the gun on and the spurs; that was a boyhood dream."
"I was just going, 'I'm an Englishman playing a cowboy, a lead in a cowboy movie. I need all the help I can get,'" Craig said. "I would figure Harrison Ford would be the man to help me out."
"It's all in the hat," joked Ford.
But of course he is the silver screen's ultimate modern cowboy, a persona developed in his roles as the brash Han Solo in the original "Star Wars" trilogy and then as the rugged, brave Indiana Jones.
Which is why it's a bit surprising that he's never played an actual cowboy before. "There's a lot of cowboy in Han Solo; there's a lot of cowboy in Indiana Jones," he admitted. "There's a little American in it, and a little of being an American is the cowboy in us as a culture."
Such an iconic form of cinema with its "don't-fence-me-in" landscapes and rough and tough characters, Western films struck a chord with the actors of "Cowboys and Aliens." As Ford and Craig pointed out, the beauty of a Western is developing relationships on screen "without the words."
"There's a sort of simple ethic that the western man lived. It really was self-reliance," Ford said. "It was simple rules: finish what you start, do the best job you can, be a good worker. They were work ethic rules, really. It's nice to do a film that has...a simplicity and straightforwardness, something really sort of black and white."
"It's a classic American form," said Favreau. "And it's opera. It allows you to tell these sweeping stories and it allows you to really focus in on character arcs and moral struggles that characters are having."
Favreau said that he wrote a Western following the success of his breakthrough 1996 film, "Swingers," and had been trying to get one the big screen ever since. Though "Cowboys and Aliens" involves intergalactic war, Favreau said he wanted to "maintain the structure of a Western and the sensibility of a Western" for his debut into the genre.
"The West is big and people feel small in this type of backdrop and, I think, accentuating the smallness of people is what makes the struggles, the character struggles, in a Western, really resonate," he said. "The aliens give ["Cowboys and Aliens"] an opportunity to open it up and make it something that's a little bit original, a little different, but we never wanted to give up that ground that was the Western tradition."