Martin Starr laughs long and hard when the Straight asks what in the hell his film is supposed to be about, exactly.

“You’re still trying to figure it out,” he replies, after collecting himself a little. “Well, it’s gonna be awhile.”

Any viewer will come away from Infinity Baby wondering the same thing. The relentlessly droll comedy begins with the premise, such as it is, that stem-cell research has led to the accidental creation of human babies that don’t age, a blunder that has, naturally, been converted into a sales opportunity by the well-known global corporation responsible. (Stick around for an after-credits sequence to find out which one.)

Enter Starr and the great Kevin Corrigan (The Get Down) as Malcolmand Larry, respectively, two slovenly Infinity Baby delivery guys who are also, it gradually transpires, life partners. Not that the relationship seems all that solid, since Malcolm is more the heterosexual type while Larry leans largely toward gay alcoholic bully.

“For me, the character was a moral compass for a movie that had no moral direction at all,” Starr explains, calling from Los Angeles (in the “small, crooked, penis-shaped state” of California).

“I’ve played someone who’s naive,” Starr continues. “But I think he’s not just naive; he lacks the basic understanding that I think most people wake up every day and explore their world with. He doesn’t quite have that. And he isn’t like a victim. He enjoys the relationship that he has with Larry. So I was like, ‘I dunno where to pull this from in my experience.’ Those are things that made me wonder if I could do this.”

Starr and Corrigan deliver a deeply entertaining two-hander full of weird and surprising rhythms and, like the rest of the film (which opens Friday [November 10] ), moments you couldn’t possibly anticipate.

Elsewhere, Nick Offerman feasts on his role as sociopathic corporate boss Neo, while Kieran Culkin has just as much fun as the relationship-phobic man-child Ben. Perhaps best of all is Megan Mullally’s turn as Ben’s monstrous bitch of a mother, Hester, whom he uses to shoo off girlfriends once the thrill is gone (immediately, on average).

Everybody here is an infinity baby, in the sense that none of these characters is much of a fully formed or terribly responsible adult. It’s all very much in tune with the sensibility we’ve come to expect from Austin-based indie auteur Bob Byington, with whom Starr has been trying to collaborate for some time now.

“He’s an odd character, in a great way,” says the Silicon Valley regular, reporting that he and his director have possibly been working the offbeat chemistry a little too much. A Q & A following a screening of Infinity Baby at the Milwaukee Film Festival in October prompted tweets complaining that Byington and Starr “could not have hated being in Milwaukee more”.

“They just didn’t understand, perhaps, our humour,” he says with a chuckle. “I had a great time. People don’t realize how much effort it takes to get in an airplane and actually go to Milwaukee.”