IN THE just-released New Zealand film Two Little Boys, Melbourne radio and television comic Hamish Blake - one half of the successful duo Hamish & Andy - has a mullet, the beginnings of a gut, swears a lot and cheerfully dismembers a corpse with an axe. In other words, he has become an actor.

''My overwhelming motivation for a lot of the scenes was not to let everybody down,'' notes the drily exuberant 30-year-old. ''Everybody else there constantly worked on films and they all clearly knew what they were doing. For them it was a process to work through, whereas I'd never been in a film before.''

Blake actually did have a small role in the Peter Helliar-devised 2010 Australian comedy I Love You Too, although he admits that was another example of where posing as an actor left him decidedly nervous. As a hotel bellhop, he shared the screen with the talented American actor Peter Dinklage (Game of Thrones) and felt compelled to make a good impression for Helliar's sake.

''I had to pretend to know more about acting when I was talking to Peter Dinklage off camera that day because I didn't want one of the best actors in the world - that's Peter Dinklage, not me - coming here and realising that Pete had cast a friend who couldn't act in his film,'' Blake says. ''I may have lied about other films I'd done and mentioned some workshops with Baz Luhrmann.''

Blake was more of an equal with his Two Little Boys co-star, Bret McKenzie, who was also on sabbatical from a well-known pairing, New Zealand's nebbish songwriters and sitcom stars Flight of the Conchords. McKenzie was as inexperienced a film actor as Blake, and their lack of overt technique suits a black comedy about the increasingly nightmarish burden of being someone's best friend for life.

In the movie, directed by Robert Sarkies and adapted from his brother Duncan's eponymous novel, McKenzie plays the ineffectual Nige, a resident of Invercargill in New Zealand's South Island in the early 1990s whose humble efforts to get his life on track are derailed after he accidentally kills a Norwegian backpacker. Panicked, he turns for help to his former best friend, Blake's Deano, who sees a chance to reclaim his platonic soulmate no matter what the cost.

''The dynamic of the film is anti-buddy - it's essentially a break-up movie for a heterosexual male friendship,'' Blake says. ''It's about possessiveness, control and tension. Deano is borderline psychopathic.''

Deano's exuberant bogan embrace of body disposal and other crimes builds on Blake's accepted comic persona, as a cheerful fantasist who refuses to deviate from what he believes no matter how bad it gets. On radio that makes self-delusion amusing, but in the movie it veers into the uncomfortable and the threatening.

''The darker it got the more intrigued I got. From a personal level it was so different that I didn't quite know at first what to do with it,'' Blake says. ''In terms of heroes of mine, the Will Ferrells and the Bill Murrays, I find it fascinating when those guys do something a little bit more serious, but my intention wasn't to be the Sad Clown.''

Blake auditioned for the part, subsequently meeting McKenzie so the filmmakers could assess their chemistry. As the shoot progressed and the narrative crept up on Coen brothers territory, the two found themselves becoming good friends as the plot became darker for the neophyte leads.

''There were times that we just looked at each other and said, 'Did that feel OK for you? Your acting was good. Could you tell I was acting?''' Blake says. ''We had this running joke that acting was this elusive thing that we hoped we were doing.''