First, I say to Jemaine Clement, I’d like to apologise for being Australian. “Apology accepted,” responds Clement. “But I find the things we made fun of about Australians [in Flight of the Conchords] very endearing. I love how much people swear there. I love the stupid ways you abbreviate things.”

Clement’s not afraid of his nationality, if his natural Wellington accent in Jim Strouse's new romantic comedy People Places Things is anything to go by. Clement plays Will, a struggling cartoonist torn between his ex-partner, played by Stephanie Allynne, and a possible new one, played by Regina Hall. Then there’s the complicating factor of his two kids, and the ex’s new fiance.

People Places Things mines the neuroses of New York City in the tradition of everything from Woody Allen films, to Lena Dunham's Girls. It’s a well-trodden path, but it’s a heartfelt one in this instance, and Clement is on form. He’s better at playing a dumped, struggling artist, struggling with single fatherhood than he ought to be, given he’s the opposite of all of these things. And his deadpan delivery makes the script as eminently quotable as any dry Concords one-liner: “I’m fine. I’m just having a ... bad life. It’ll be over eventually”.

Throughout the film Will vents his frustrations through autobiographical comic strips. It’s a career path a young Clement dreamed about. “Maybe at one stage, I wanted that to be me,” he says. “When I was about 15. But I’m not good enough.”

He talks about being the leading man in a critically acclaimed drama like it’s a holiday. “I don’t want to publicise this too much,” he says, “but acting isn’t that hard. The hours are terrible, but otherwise, you’re just saying stuff.”

This is selling himself short, of course. He’s a naturalistic and charming performer, and as a 40-something New Zealander, he’s not a typical leading man for American cinema. “I guess not,” he concedes. “I’ve read that.”

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There are similarities between Will in People Places Things and Jemaine, the bizzaro version of himself he plays in Concords. Both are flailing artists in New York. Both are unwilling to accept an adult’s lot.

“They’re the only two acting roles I’ve had where I’ve used my natural voice,” says Clement. “So I did have to stop myself from falling back on the Jemaine character.” But, he says, that’s where the similarities end. “Jemaine is far more needy and cowardly and manipulative. Bret and I consciously played our Concords characters as a seven year old and 10 year old. This guy isn’t weirdly immature like that.”

Indeed, this character has two daughters, and he’s a charmingly natural dad, much to the chagrin of his ex, who says he’s only good at having fun with them.

But a man who scrapes together a living together writing comedy songs, and a man who scrapes together a living drawing comic strips, as adult responsibility looms? Is this crossover a reflection of the infantilisation of a generation? Is the popularity of characters like this a sign that, generation by generation, we’re becoming manchildren?

“In a way, the manchild thing is probably why this generation of dads is perhaps better than the last,” says Clement, “or at least more natural. They relate to kids better. Dads spend a lot more time with their kids than they used to, and they don’t mind being childish.

“There’s no clear line between childhood and adulthood anymore,” he says. “It used to be that you were a kid, and then you were a man – and a man was someone who belted his kids and had PTSD. It was probably not a healthy division.”

And what’s being an actor if it’s not just a massively expensive game of dress-ups? Clement’s in no position to deny that comparison. He just finished on the set of Steven Spielberg’s version of Roald Dahl’s The BFG, which involved wearing a skin-tight bodysuit and acting with toy cars on a green screen set in post-production, so he can be motion-captured in as a giant.

And what adult thinks that doesn’t sound pretty fun?

People Places Things opens Thursday September 10.