Here’s Exactly How Mark Ruffalo Transformed Into Twins For HBO’s ‘I Know This Much Is True’

Mark Ruffalo plays identical twin brothers in HBO’s new drama I Know This Much Is True. Audiences may take it for granted now that shows like Orphan Black and movies like Multiplicity, Adaptation and The Nutty Professor allow actors to play multiple roles in a single scene. However, Ruffalo had a additional challenges playing both Thomas and Dominick Birdsey.

Mark Ruffalo and Mark Ruffalo
Mark Ruffalo and Mark Ruffalo | Atsushi Nishijima/HBO

Thomas has paranoid schizophrenia and Dominick attempts to care for him. Ruffalo looks noticeably different in each role. Ruffalo and Derek Cianfrance, who adapted Wally Lamb’s book and directed I Know This Much Is True were on a Television Critics Association panel for the HBO series in January. They discussed the extent of technology and performance that created both characters. I Know This Much Is True airs Sundays at 9 p.m. on HBO.

Mark Ruffalo spent five weeks transforming into Thomas in ‘I Know This Much Is True’

Cianfrance said that they filmed all of Dominick’s scenes, and his portions of scenes with both brothers, in 15 weeks. Ruffalo then took five weeks off, shaved his facial hair and gained 30 pounds to play Thomas. So, he filmed the opposite side of each scene at least five weeks apart.

Mark Ruffalo as Dominick
Mark Ruffalo | Atsushi Nishijima/HBO

“We didn’t want it to be like I run and put a wig on, and then run and do the same scene on the same day,” Ruffalo said. “We took five weeks off to really separate these two guys. Thomas was on a lot of medication. He needs medications. These mood stabilizers and antipsychotics cause people to put on weight. It was important for us to really, really have these guys be two different people.”

Mark Ruffalo did more than gain weight to play Thomas

Physical transformations always get a lot of attention because you can see them like Robert De Niro in Raging Bull or Charlize Theron in Monster. Ruffalo said he took on the psychology of Thomas’s condition too.

Those five weeks were really kind of lonely. He hears voices, and just kind of like imagining that life. There’s a couple weeks where I was just by myself in the place I was staying up in Poughkeepsie going down into the heart of this mental illness and studying it. Spending time in institutions, what these kinds of medicines actually do to you physically and mentally, how the obsessive nature of it manifests itself.  Then the quality, his emotional quality which is softer, which is more vulnerable and how that manifests in your body. I can get more deeply into that later, but there’s definitely two different people there.

Mark Ruffalo, Television Critics Association panel, 1/15/2020

‘I Know This Much Is True’ had another Thomas and Another Dominick

Whenever there was a scene in I Know This Much Is True with both brothers together, Ruffalo still acted opposite a costar. Gabe Fazio played Dominick when Ruffalo was Thomas, and Thomas when Ruffalo was Dominick. Cianfrance didn’t want Ruffalo to treat him like a generic double.

“I told Mark, ‘He’s your brother,’” Cianfrance said. “‘When you’re Dominick forget that you’re ever going to be Thomas. When you’re Dominick this is your brother.’ Gabe completely played that role and we shot the scene as we would shoot any scene.”

Derek Cianfrance used various techniques to combine both Mark Ruffalos

Ruffalo spends his Marvel movies wearing a performance capture suit to play the Hulk. So he has experience with visual effects. Cianfrance had a whole bag of tricks he could use to combine both sides of the scenes Ruffalo would shoot as the twins. 

I Know This Much Is True
Mark Ruffalo and Mark Ruffalo | Atsushi Nishijima/HBO

“We shot it very, very simply,” Cianfrance said. “A lot of it is shot/countershot. So, Mark is Dominick, is having a scene with Gabe as Thomas, and then all these months later we just had to match certain things with the lighting. We had specific measurements, and sometimes we add motion control. There’s not one way that we did it.” 

Gaining 30 pounds was not fun

Ruffalo did transform his body to distinguish Thomas. He expected that to be more fun than it was. 

“Actually putting on the weight for Thomas was really challenging,” Ruffalo said. “I didn’t expect it to be. I thought I was going to be having a fun time doing that. When you’re force feeding yourself, some of the romance of food sort of leaves.”