100% genuine

Joseph Gordon-Levitt has been performing since before he mastered addition. He lives in Los Angeles’ eclectic Silver Lake neighborhood and in his spare time, he wanders around town with a video camera in hand, making short films. But he wants to be clear, he’s no hipster.

“I think a hipster is someone who is trying to be hip with no substance behind it. And personally, I don’t think that applies to me,” said the actor, 30.

Gordon-Levitt’s performance as Adam in the upcoming terminal illness buddy comedy “50/50,” opening in theaters Friday, confirms the guy has gravitas. In the film, based on the true story of its screenwriter Will Reiser, Gordon-Levitt plays an unfulfilled 25-year old whose life is upended when he learns he has spinal cancer. His best friend Kyle (Seth Rogen) tries to offer support, but Adam finds an unlikely ally in the young psychiatrist assigned to help him cope with treatment (Anna Kendrick).

“It’s really rare to find a story that has characters that feel like human beings,” said the actor of what immediately struck him about Reiser’s screenplay. “In most scripts, the characters feel more like stereotypes or plot devices and this felt really earnest and real. And it was genuinely funny. It made me laugh and the hardest thing to find is writing that is actually funny.”

Seated in a makeshift green room directly behind the movie screen at Toronto’s Ryerson Theater, Gordon-Levitt is a bit road-weary, having just flown in from Los Angeles, where he had spent the preceding night working on Christopher Nolan’s upcoming Batman sequel “The Dark Knight Rises,” in which he plays a mysterious Gotham City policeman named John Blake.

But his energy waxed later in the evening, when “50/50” received a raucous standing ovation from the Toronto International Film Festival audience assembled for its premiere. With its union of humor and pathos, “50/50” offers audiences both a more sophisticated take on the typical Hollywood bromance, yet enough bawdy humor to lure in Rogen fans adverse to a film with cancer as its core.

Also working in its favor is Reiser’s own happy ending. He’s alive and healthy and was on hand for the film’s premiere, where he stood proudly next to Gordon-Levitt.

One of the few performers to successfully transition from child star in the ‘90s sitcom “3rd Rock From the Sun” to respected working actor, Gordon-Levitt has carved out a career in critically acclaimed independent films such as “Mysterious Skin,” “Brick” and “(500) Days of Summer,” in addition to appearing in big-budget studio fare including last year’s high-minded “Inception” and the action flick “G.I. Joe: The Rise of Cobra.”

Among his male contemporaries, Gordon-Levitt might be compared only to “it” boy Ryan Gosling in terms of his willingness to take risks and his ability to go dark and edgy or lighter and more accessible.

It was Gordon-Levitt’s resume that made him the first choice to play Will -- or more accurately, the first choice to replace the movie’s original star James McAvoy, after a family emergency forced the British actor to leave the production only a few days into filming.

“On Friday we realized we had until Monday to find a new actor or the movie had to shut down,” said Rogen, who produced “50/50” and is one of Reiser’s closest friends in real life. “Will and I were living together at my parents’ house in Vancouver and Joe was the first name we came up with. Joe came up through comedy so we knew he was funny, and the movies he had been doing lately were dramatic and awesome.”

Plus, Reiser chimed in, during a joint phone call following the festival, “We really couldn’t think of anyone else.”

Fortunately for them, Gordon-Levitt agreed to read the script and within a week he was on the Vancouver set shaving his head for the first scene he shot for the movie.

“You can only shave your head once. There was no take two,” said Gordon-Levitt of the scene, which is featured prominently in the marketing materials for the film. “That made it really exciting and a great kickoff into the job.”

Despite his eagerness for the role, Gordon-Levitt -- who lost his older brother, Daniel Gordon-Levitt, last year, and a friend to cancer when he was 18 -- was careful to keep some separation between himself and his character, who while undergoing chemotherapy is also dealing with a deteriorating relationship with his girlfriend (Bryce Dallas Howard) and an overbearing mother (Anjelica Huston).

“Sometimes I’ll really let myself go into a character -- in this movie, I always kept a little life line, ‘this isn’t true, I don’t have cancer,’ ” Gordon-Levitt said. “Because I think this stuff is powerful and can be self-fulfilling sometimes, I consciously kept a little light on that this was all fiction.”

The comedy in the script helped keep the atmosphere on set light. Rogen’s Kyle, who has some trouble coming to terms with his friend’s mortality, uses Adam’s diagnosis as an opportunity to pick up women and smoke medical marijuana. Gordon-Levitt said he specifically appreciated the scenes involving the friends’ awkward hook-up attempts.

“There are not nearly enough movies that show how the mating ritual is really just... not sexy at all,” Gordon-Levitt said. “I know when I was younger, before I had a lot of those experiences, I bought into some of the fantasies that Hollywood sells about romance and sex. This movie says don’t believe the hype. You don’t have to have cancer to have nights like that, nights that are totally lame.”

After the “50/50” screening, the Los Angeles native hosted a late-night event in Toronto titled “hitRECord at the Movies with Joseph Gordon-Levitt” as part of his moonlighting gig as head of the online production company “hitRECord,” which he founded with his late brother, a performance artist who went by the name Burning Dan.

There was no sign of exhaustion as the lanky actor commandeered the stage, riffing on the videos he created with his online partners and bringing audience members to the stage to participate in readings that would likely make it into later pieces.

Gordon-Levitt, who will next star in the bike messenger actioner “Premium Rush,” is currently working with Nolan for a second time -- before he joins Steven Spielberg on the set of the period drama “Lincoln.” But it was when he talked about hitRECord that he became the most exuberant. Having acquired a video camera at a young age, the actor explained that he used to tell himself to “Hit Record” as a reminder to be creative, whether it was writing songs or stories, or making short films.

Now he regularly emcees live shows -- like the one he scheduled in Toronto -- to show off the site’s efforts. He just released its first anthology of work, titled “RECollections” and scored a book deal for the company’s literary efforts.

“Making things in all sorts of ways is what I love to do. It’s my therapy, it’s my everything. I just can’t wait around for someone to hire me,” Gordon-Levitt said. “That round REC button became a symbol, a metaphor for taking things into my own hands and doing it.”

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nicole.sperling@latimes.com