"This role is very different from anything I've played in the past, and that in and of itself was a huge draw for me," Franco tells PEOPLE.
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Dave Franco got to show off a new side of himself in his first major dramatic role in the Netflix drama 6 Balloons, but playing a junkie in the film also took its toll on the actor.

In his latest film, the usually comedic actor turns in a gritty performance as a degenerate heroin addict and young father named Seth who leans on his sister Katie, played by Broad City’s Abbi Jacobson, to help him find a detox center as he suffers from withdrawals over the course of one night.

“This role is very different from anything I’ve played in the past, and that in and of itself was a huge draw for me,” Franco, 32, tells PEOPLE. The Now You See Me star says he took on the project hoping that “people would start to see me in a different light and start to envision me in different types of roles.”

Still, Franco says the part was daunting. “I was very nervous for many reasons,” he says. “First off, I knew that I was going to have to go through a huge physical transformation. I ended up losing about 25 pounds in a very, very short period of time.”

While Franco says he usually doesn’t have trouble detaching himself from his roles, the film’s physical demands were hard to shake off. “When you lose that much weight it affects you,” he says. “I was depressed while we were filming this movie.”

At one point during filming, his wife Alison Brie called him out for bringing the work home with him. “I came home and my wife Alison called me out and said you’re not yourself, you’re not fun to be around,” he says, adding with a laugh, “I said I’m f—— starving what do you want from me?” Franco and the Community actress began dating in 2012 and announced that they had married in a private ceremony last March.

Even after enduring the demanding shoot, the effects of the weight loss lingered. “I was running so much to lose the weight that after we finished filming I had to go to physical therapy for a couple months because I had hurt my knee from all the running,” he says. “It was brutal in every way but I hope people like it and hope it was all worth it.”

Prepping to play a heroin addict took a mental toll on Franco as well. “The whole research process also contributed to why I was so depressed. You can imagine how hard it is to watch several documentaries about heroin addicts every single day,” he says. “I felt like I was in this dark heroin tunnel for a couple months, and I was just not the most fun person to be around. I commend everyone on set who is still friends with me, because I really was off in the corner by myself not talking to anyone.”

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Starring alongside Jacobson, who was also making her first foray into drama, helped Franco feel more comfortable, and their comedic background helps inject some much needed humor throughout the film. “I think one of the reasons that Marja-Lewis Ryan the director thought of the two of us for these roles is because the film needs some levity, so it’s not just one heavy scene after the next,” he says.

“I think our humor actually sells the fact that we are brother and sister, and you can buy into our history,” he adds. “Even during these really heavy circumstances we’re still able to make fun of each other and find the humor in these dark moments, which feels very familiar.”

Franco says he was also drawn to the role for its realistic depiction of how drug addiction can effect people from a variety of socio-economic backgrounds. “A huge criteria for how I choose roles is that I want to be involved with projects that at least feel like they’re attempting to bring something new to the table,” he says. “We’ve all seen movies about heroin addicts before, but I’d never seen one about a heroin addict who came from an upper-middle class family and seemingly has no reason to resort to these hard drugs.”

To prepare for the role, Franco spent time with the person his character is based on, who happens to be the brother of one of the film’s producers. “He was working in a law office while he was he at his lowest point,” Franco says. “During lunch he would go down to Skid Row and shoot up. So there is such thing as a functioning heroin addict and that’s not something that we often explore in film. I think that something a lot of people will take from this movie is the fact that this can happen to anyone.”

6 Balloons is available to watch on Netflix now.