Interview: Jesse Eisenberg and Kristen Stewart talk about American Ultra

American Ultra is one of the funniest, most action-packed films of the summer, and much of its humour comes from the unlikely casting of Jesse Eisenberg as a stoner who morphs into a killing machine.

Eisenberg just laughs at the notion that he might ever play such a role. "Oh yeah, when my mother gave birth to an undersized premature baby with an androgynous name, I'm sure she thought I'd grow up to be a big action movie star," he says during a recent telephone interview that also features co-star Kristen Stewart.

But Eisenberg and Stewart say they saw something special in the script by Max Landis, the son of John Landis, who directed such classics as Animal House, The Blues Brothers and the Michael Jackson video Thriller. In essence, the movie is a mash-up of 1980s and '90s genre films, with inspiration from The Terminator and Reality Bites.

"Landis grew up in the world of movies, so he's referencing other movies - and referencing them in a way that makes them great," Eisenberg says. "There's a modern sense of irony and self-awareness."

And Eisenberg and Stewart were eager to work with director Nima Nourizadeh, whose best-known previous film was 2012's surprise hit Project X.