Preview: Step Brothers, cinemas across the UK

Hollywood's new kings of comedy

John C Reilly is ranting. The 43-year-old actor is furious about some of the less-than-complimentary reviews of his new film, Step Brothers, a brash comedy about two overgrown adolescents still living at home. "We were in some way commenting on real things in this movie. Things like family relationships and this phenomenon of the man-child. We were trying to talk about what it's like to be in America right now and how spoilt we are."

The "we" in question is Reilly, co-star Will Ferrell and director Adam McKay, the trio who previously collaborated on 2006 Nascar comedy Talladega Nights: The Ballad of Ricky Bobby.

In this latest movie, Reilly plays Dale, a 39-year-old who is forced to share his living space with Ferrell's similarly stunted Brennan after their single parents get hitched. It's yet another example of how Reilly has recently followed Ferrell into the laughter business, be it a role in the late Robert Altman's gentle ensemble A Prairie Home Companion, a cameo in Tenacious D – The Pick of Destiny or his Golden Globe-nominated lead in this year's music bio spoof Walk Hard: The Dewey Cox Story. "It just happened," he says, shrugging. "I wish I could say I had some master plan for what I was doing with my career."

It's been an idiosyncratic 20-year run, ranging from a small role in his 1989 debut Casualties of War to critically acclaimed parts in movies such as Magnolia and Boogie Nights. Now Reilly is joining the mainstream with a vengeance – Step Brothers has been produced by Hollywood's current king of comedy, Judd Apatow.

Quite what truth Step Brothers tells is hard to say. Boasting the sort of script that makes Viz look sophisticated, Step Brothers is certainly vulgar: Brennan is made to lick dog excrement by some bullies in one scene while he rubs his testicles on Dale's drum-kit in another. Meanwhile, when Dale goes for a job interview, a bout of flatulence puts off his prospective employer.

"An actor's life is really dictated by what opportunities come your way," Reilly explains, "and also what audiences want to see."

'Step Brothers' opens on Friday