At the show’s Television Critics’ Association press tour panel, Ruffalo said that the character of Thomas has a mental illness which means has has to take “stabilizers and antipsychotics” which cause him to put on weight. Ruffalo shot the scenes where he played the other twin, Dominic, before putting on the pounds over a five-week period of force feeding.
“When you’re force feeding yourself some of the romance of food leaves,” Ruffalo said. “Those five weeks were kind of lonely, I’d been a way from my family and (Thomas) hears voices, and I was imaging that life and there was a couple weeks where I was just staying by myself, going down into the heart of this mental illness and studying it.”
“I Know This Much Is True” follows the parallel lives of the twin brothers in a story of betrayal, sacrifice, and forgiveness, taking place against the backdrop of 20th century America. The series is based on the book of the same name by Wally Lamb, and Ruffalo said he felt a lot of pressure taking on both roles and the mental illness part of Dominic’s character in particular.
“There’s an element of mental illness in this project and you want to be as honest as you can to that, and it means a lot to me to be honest to that which means going into that world and getting to know it and getting comfortable with it,” Ruffalo said. “I was really afraid to play it, I think it’s a really an important issue and I want to tell it as honestly as possible, the responsibility of playing it was really apparent to me.”
In terms of the difference between the two brothers, Ruffalo said that Dominic is much more “bound to our ideas of manhood and masculinity,” while Thomas is more “sensitive and open” because he relates more with his mother.
As executive producer, writer and director Derek Cianfrance put it, the brothers “have the same DNA, but they 40 years of completely different life experiences.”
Cianfrance said that another actor played both twins when Ruffalo was in the opposite role, and that he shot the series “very simply,” shot-counter shot, in order to not have in order to avoid the technical challenges overwhelming the story and the characters.
In terms of inspiration for the series, Cianfrance pointed to the famous dinner scene between Robert De Niro and Al Pacino in Michael Mann’s “Heat.”
“They’re never on screen together….(Mann) was creating flip sides of the coin, you can’t see the head and the tail together,” he said.
The series also stars Melissa Leo, Rosie O’Donnell, Archie Panjabi, Imogen Poots, Juliette Lewis, and Kathryn Hahn.