PATTON OSWALT has played everything from a French epicurean rat to a table tennis master named The Hammer, but none of his dozens of screen roles could have prepared him for his turn in the critically acclaimed, often darkly comic indie film "Big Fan."

"I didn't expect how much I really had to trust in the material and not try to constantly take it where I thought it ought to go," the L.A.-based comedian said over the phone. "I had to trust the other performers way more than I thought. In a way it was freeing, and I didn't think it would be that way."

Oswalt plays the titular fan, an obsessive New York Giants follower whose life is turned upside down after a chance encounter with a star player. And though it's directed by Robert Siegel, who wrote "The Wrestler," it's far from Oswalt's first brush with the big time.

He also provided the voice of Remy the Rat in the Oscar-winning Pixar film "Ratatouille," and appeared as Kevin James' buddy, Spence Olchin, in more than 120 episodes of "King of Queens" for nine years.

But "Big Fan" is Oswalt's biggest dramatic role yet, and his numerous smaller appearances in shows like "Reno 911!," "United States of Tara" and others have been means to an end for his stand-up career.

"I just want to do stuff that to me is challenging and fun and original," Oswalt said. "That's all that matters to me as a performer."

That's clear to anyone who has paid attention to

His third and most recent CD/DVD, "My Weakness is Strong," continues the hot streak with more randomly insane stories, sci-fi references and surprisingly mature takes on relationships.

"It's not what it's about, it's how it's about it," Oswalt said. "Nothing that I did on other albums was all that original, subject-wise, I just tried to do different takes on it."

Even though Oswalt's subject matter remains both fearless and unapologetically geeky, for "My Weakness is Strong" he jumped from Seattle indie label Sub Pop to Warner Bros. Records.

"I wanted to know if I could thrive on a major label," he said. "It was an itch I wanted to scratch."

Oswalt, however, isn't doing an extended national tour to promote "My Weakness." He remains a busy character actor in films like "Observe and Report" and, most recently, Steven Soderbergh's "The Informant!"

After the critical success of "Big Fan," he's also willing to take on meatier roles.

"I would totally do something (like 'Big Fan') again," he said. "I have a lot more confidence now as an actor because I just put my trust in the director and the other actors around me more than I ever could in the past."