NEW YORK • Four and a half years ago, Leslye Headland went on a blind date of the working variety with Jason Sudeikis, a man she knew only as "that goofy guy from Saturday Night Live".

Each had been toiling on a project that would unleash a foul-mouthed assault on gender politics: He as a star of Horrible Bosses (2011), about three harassed workers plotting to murder their employers. She as the writer and director of Bachelorette (2012), about an alpha girl who snaps when a high-school bestie - the one she christened Pigface - beats her to the altar.

Three hours later, "I was like, 'Who is this guy?'" Headland said. "I'd never met somebody with such old-school Hollywood charisma. I felt like I was the only person he had ever talked to. And it was such a stimulating conversation, about everything from art to life."

Inflamed by artistic passion, she composed a romantic comedy for him.

"I was incredibly flattered," Sudeikis said. "And I was really moved by the story. I thought it was a great take on a genre that's been celebrated and beloved but also trashed and commodified. And the idea of whether, as the old song goes, lovers can be friends or vice versa."

Sleeping With Other People, opening in the United States on Sept 11, propels him into heartthrob territory after a career in which, wielding a smirk and a smart retort in films such as We're The Millers (2013), he had become pigeonholed as what A.O. Scott of The New York Times called "a genial, excitable doofus who also happens to be catnip for the ladies".

Headland padded that caricature with the most potent qualities of Sudeikis' off-screen self - courtliness, a seductive intelligence - while mining her own romantic travails to write the role of Jake, a Columbia student who loses his virginity late, only to morph into a womaniser.

Flash to the present, where Jake and Lainey - his partner in deflowering, now a serial cheater, played by Alison Brie - encounter each other at a 12-step meeting for sex addicts and go on a sort-of date. Fearing a backslide into old habits, they spend the rest of the film trying to subvert their lust. It is unabashedly romantic and deliriously raunchy, a bonbon for a hook-up generation longing for deeper intimacy but searching for it in the wrong places.

"In a film that was meant to dig into what was wrong with the rom-com genre and update it, you needed a Jack Lemmon you wanted to" have sex with, Headland said, using saltier language. "It couldn't just be Billy Crystal or Bill Pullman or someone who felt safe. You needed a dangerous guy who was also super, super lovely."

"Jason," she added, "is always going to have that glint in his eye no matter what you have him doing."

There certainly is something about Sudeikis. He arrived at The New York Times building practically incognito, a full beard and baseball cap shielding his face, a Leica M3 camera slung across his shoulder.

He took his time settling into the conversation, the distance narrowing as he revealed himself: an affection for Kansas, where he grew up. An adolescence fuelled by sports. A basketball scholarship and the realisation that he loved improv more.

A 1997 move to Chicago with a singular goal, to attend the Second City conservatory, which he did before joining its Las Vegas company and performing sketches by Steve Carell and Tina Fey until the producers gave him permission to write his own.

Then, in 2003, came SNL. He was hired as a writer and battled to have his sketches on the air, while aching for a chance to perform.

Then, in his third season, there he was, making a name for himself in memorable skits with Kristen Wiig and parodying ESPN Classic announcers with Will Forte.

Forte said he and Sudeikis were a contrast in styles. "I'm a real overthinker and he has these amazing ideas, but we meshed well together," said Forte, whose Fox series, The Last Man On Earth, features a recurring guest turn by Sudeikis. That commitment to collaboration was apparent on the set of Sleeping With Other People.

"Leslye was like, 'I don't want it to come off creepy', and we all worked together to find that balance of it being friends while actually being kind of sexy," Brie said. "A lot of that is owed to the humour that Jason infuses into the scene but also just a naturalness with which he makes everybody comfortable."

That Sudeikis turns 40 next month might partly explain his desire to take on more emotionally resonant characters.

So might his engagement to actress Olivia Wilde (following his 2010 divorce from writer-actress Kay Cannon) and the birth of their 16-month-old son, Otis.

He said: "I was going through a personal journey before meeting Olivia, similar to Jake's; trying to figure out how to allow myself to be loved after the death of a relationship. Coming out of singledom and getting to fall in love with Olivia in New York - that's probably all in the film." NEW YORK TIMES