Everything happens for a reason. The phrase is loosely used, but in the new film “Jeff, Who Lives at Home,” Jason Segel’s character believes it.

It’s about a 30-year-old man named Jeff who lives in his mom’s (played by Susan Sarandon) basement. He has no job. No real relationships. Not even with his older brother, Pat (played by Ed Helms), who also yearns for emotional fulfillment.

But in this seemingly hopeless reality, characters in “Jeff, Who Lives at Home” then become unlikely heros.

“Those are inherently I guess sad or dark situations, but for us, at the end of the day, we just love these guys so much and we root for them and we want them to win,” said writer-director Mark Duplass in a March 2 conference call.

The movie takes place over the course of one day, and with each moment Jeff finds continual signs from the universe depicting his destiny.

The making of this film, too, could have been fate’s doing. Segel said he was surprised with whom was actually directing the movie.

“I have legitimately thought it was the Hughes brothers and then when I arrived on set it was clear that it wasn’t,” he said, laughing. “But it was still a worthwhile experience.”

But “Jeff, Who Lives at Home” isn’t your typical Segel and Helms film. It’s bordered between comedy and drama, consistently aligned with the Duplass brothers’ darker comedic feel. The honest tone of the movie is one Helms said he has never quite done before.

“This movie doesn’t shy away from the kind of painful aspect of a dysfunctional life,” Helms said in a Feb. 17 conference call. “So it might be a little bit different than what people expect, but I hope in a good way. Kind of a nice little treat, if you will; a little twist on the expectation.”

And with big-name actors such as Helms, Sarandon and Segel, comes a big budget to make the film and an even bigger chance to get star struck. Writer-director Mark Duplass said in a March 2 conference call that, while meeting Helms and Segel was nerve-racking at first, since they are closer in age it made the situation easier to adjust to.

It was Sarandon who gave these men the jitters.

“All of the sudden, this sort of screen legend/goddess who, make no mistake about it, is like smoking hot comes down and descends on our set,” Duplass said. “And we’re just like, A: ‘Don’t want to embarrass ourselves in front of her’ and B: ‘Don’t want to offend her with our juvenile filmmaking tactics.’”

He added, jokingly, that there were enough takes of Segel salivating to Sarandon that it could be made into a “whole other movie.”

Segel admitted it was in part because of his longtime crush on the actress.

“I was in awe the whole time,” Segel said.  Any time you get to work around somebody that you’ve admired for so long, there’s a little part of you that feels like you’ve made a little bit.”

“Just to suppress that I was wildly attracted to the woman playing my mom was easily the hardest part of the movie for me.”

And while the chemistry between the actors was “fantastic,” Helms said the film presented challenge he had yet to face.

“We had an amazing time working together,” he said. “But it wasn’t always about finding the laughs, it was kind of a new challenge for me because it was about finding realism and authenticity.”

This includes the “juvenile filmmaking tactics” Duplass referred to, which includes the employment of on-screen improvisation.

While Helms said the filmmakers wrote “down to the word, a wonderful, compelling, hilarious and moving script,” by the time filming wrapped, only half of the original script made it into the movie. The rest is captured moments, created by the actors.

“Every single line of dialogue, every single moment is improvised to a certain extent,” Duplass said. “That doesn’t mean that the script changes drastically, but we are asking our actors to be in the moment and throw surprises in.”

This resulted in genuine, inspired acting.

“You just find these really kind of authentic moments and it feels real when you’re doing it,” Helms said. “And I’m sort of stunned by the result. I think Mark and Jay got something out of me that I didn’t necessarily know was in there as a performer.”

Segel said it was Jeff’s simplistic character that drew him to the role, thus making improvisation an easier task to take on.

He also said working on “Jeff, Who Lives at Home,” provided some additional benefits.

“Previous to this I had been doing a lot of writing and producing of the movies that I was doing,” Segel said. “So on this one, I got to just be invited to the party without having to prepare all the food and decorations and all that stuff. And so my job was just to show up and have a good time at the party. I really enjoyed that element of it.”

And perhaps this film won’t be the last film Segel and Duplass will do together.

“I would like to announce I’m directing ‘Jeff Who Lives At Home 2: This Time It’s Personal,’” Segel said, laughing.

Jeff Who Lives at Home hits theatres nationwide today.