Parenthood - Lauren Graham Parenthood - Lauren Graham

When Lauren Graham joined the cast of Parenthood, she brought something unexpected to the dark family drama.

"Lauren brings so much to the role," said executive producer Jason Katims (Friday Night Lights). "One of the things that she brings is an incredible humor."

Maura Tierney leaves Parenthood  

Graham stepped in to play struggling single mom Sarah Braverman after Maura Tierney had to drop out to accommodate her cancer treatments. Tierney's performance, though moving, was decidedly more dramatic. "When we went back to [reshoot], there was also a second chance to do some other things as well," Katims said. "Some of that was to lighten the tone, some was simply storytelling, making things clearer."

Graham, who had never seen the original pilot, said it was easy to find comedic moments in a series filled with such heart-wrenching drama. "The moments of depth and weight play better against the contrast of looking at things with humor," said Graham. "To me, you don't want a show that doesn't have one or the other. That's life, isn't it?"

Welcome to Parenthood, Lauren Graham

"I wouldn't be good on something where I can't have a sense of humor," Graham added. "I said to Jason, 'I can't do those lines; it doesn't feel right to me.' He said, 'Oh God, you make it yours, you do what you want.'" The actress also credits the show's "documentary" shooting style. "They set up cameras and just let us go," she added. "I'm just doing what I do the way I serve the story best. I'm a sarcastic person with a sense of irony, so that's just what I do."

Parenthood debuts on Monday, March 1 at 9/8c on NBC.