I met Mark Ruffalo in 2004, when he and co-star

I met Mark Ruffalo in 2004, when he and co-star Laura Dern were doing press for the independent drama We Don't Live Here Anymore. I told him that a few weeks earlier, he had sat next to my mother and me at a screening of 13 Going on 30. It was a thrilling experience for my mother, visiting from Oregon, who was excited she got to see a movie star. "Oh, really?" Ruffalo inquired. "Who did she see?" It took a moment to realize the question was genuine and free of irony—something rarely seen in people, let alone actors, these days. At which point Dern jumped in, slugged him on his shoulder, and said, "She's talking about you, you dork!"

Three years later, Ruffalo is attending the Toronto Film Festival with another searing family drama, Reservation Road, and says he's still "as big a dork—if not bigger." Perhaps, but he has also remained one of the best actors working today, a person whose name on the poster means the movie can't be a complete waste. Ruffalo came to Hollywood's attention fairly recently, with his breakout turn as Laura Linney's aimless brother in 2000's You Can Count on Me, written and directed by his good friend Kenneth Lonergan. The actor has been courted by some of the best directors in the business—Michel Gondry, Michael Mann, Rob Reiner, and Jane Campion—and in 2007 he worked with David Fincher (Zodiac) and Terry George (Reservation Road).

And he has done it all while maintaining a relatively low profile. In an era when the media is alerted every time Jennifer Lopez has a headache, Ruffalo would rather not address the surgery he underwent in 2002 for a benign brain tumor. Tell him it's a classy decision, and he seems surprised. "Really? I feel like people always want to talk about it," he shrugs, before adding, "Part of that was selfishness. I just wanted to go lick my wounds quietly somewhere."

What he does love to talk about—passionately and articulately—is everything ranging from performing to politics. Below are just a few of the reasons Ruffalo remains one of our favorites.

Reservation Road tells the story of two men brought together by a tragic accident. Ethan is a loving husband and college professor whose son is killed in a hit-and-run accident. The car's driver is Dwight, a divorced father trying to stay involved in his son's life. With Ruffalo and Joaquin Phoenix starring in the film, it would make sense for Ruffalo to play Ethan. But Phoenix was already attached to the role, and George wanted Ruffalo for Dwight. "I was surprised I wasn't Ethan, too," he says. "And I was terrified to play Dwight. Could I pull it off? But it was exciting for me. Because I'm the last person I would have cast for this part. When I read it, I thought of several other actors who would have been good for this part, with Joaquin being one of them—edgier guys than myself, like Russell Crowe." Ruffalo pauses before adding, "People are probably saying, 'We wish Russell Crowe had done it.'"

Not likely. It's hard to imagine an actor other than Ruffalo eliciting sympathy for Dwight. "A journalist today said, 'How do you justify playing this part? They're going to hate you and think you're a scumbag,' " Ruffalo recalls. "And I just figured that you've got to prepare yourself to be hated to play a part like that."

On the day of this interview, Ruffalo is wearing a plastic orange ribbon around his wrist. Perhaps a souvenir of some late-night party at a Toronto club? Actually, he explains, it's to show his support for Congress beginning the impeachment process against President Bush and Vice President Dick Cheney. As it turns out, the aforementioned journalist spotted the bracelet and engaged Ruffalo in a heated political debate. "It was someone very conservatively entrenched. He wanted to know why a celebrity felt he should talk about politics," Ruffalo says. "And I explained it's because artists throughout history have always spoken for the people. That's our job; that's what we do. Celebrity is one thing; an artist is another."

Ruffalo says he never aspired to movie stardom. "I'd been doing theatre, which I love, and I was just happy to have a job at all—anything to get out of bartending," he says. Frustrated by rejection, he quit acting several times over the years. "My backup career was construction painting for my father, which is backbreaking, brutal work," he says. "At one point I thought I'd get into writing and directing—as if that weren't as competitive as acting. For every 100 actors to a film, there's one director. So that was a smart move."

Things changed when he met Lonergan, who first cast him in his play This Is Our Youth, then in the film You Can Count on Me. And Ruffalo's life changed forever: "If you asked me in my early 20s if I would be sitting here today, I would have laughed at you. I didn't have the confidence, and I didn't have any grand sort of plan other than to get a job somewhere and hope somebody realized I was as good as I thought I was." Lonergan and Ruffalo recently reunited for Margaret, scheduled for release in 2008. "I saw a three-hour-and-20-minute cut of it that was so fucking beautiful, so brilliant, so moving," Ruffalo raves.

So fond are his memories of You Can Count on Me that he seems more interested in talking about his onscreen sister, Linney, who is at the festival with her film The Savages. "Have you seen it?" he asks. "Is it great? Isn't she amazing?"

A fan of the novel by John Burnham Schwartz, Ruffalo knew some changes would have to be made in filming Reservation Road. "I've worked on a lot of books turned into movies now, and I think the only way you can really approach it is that it's a completely different piece of creation. It's its own thing," he says. As a result, parts of the story about Dwight's alcoholism and abusive background were dropped from the film, although Ruffalo still used them to inform the character. "I love working on a book, because normally you sit down and you write a backstory for yourself. When you're working on a book, it's so much richer than anything you could possibly come up with—otherwise I'd be a writer," Ruffalo says.

Ruffalo also fully supports many of the updates George made to the story, including a subplot in which Ethan befriends other victims on the Internet. "That's a sign of how much things have changed. You can always get on the Internet now," he says. "Man, if they'd had the Internet and a fax machine in Zodiac, they would have caught that guy long ago!"

Aside from an Independent Spirit Award nomination for You Can Count on Me, Ruffalo has never received a major accolade for his work—unless you count the MTV Movie Award nomination he shared with Jennifer Garner for doing the "Thriller" dance in 13 Going on 30. But don't think it bothers the actor. "I don't care anymore," he says. "It's nice to get awards and all that and have nice shiny things to remind you. But thank God over the last few years it's really been about the experience of doing it. And I've been having great, tough, challenging roles."

Though many would argue that the part of Dwight is a lead role, Ruffalo says he wouldn't care if he was submitted in the supporting category, with Phoenix as the lead. "He worked more days than I did. And he's No. 1 on the call sheet," he explains. "I think it really is intended to be his story." Ruffalo has been through award campaigns with previous films, and he admits, "I don't know how any of this works. They'll sort of position you, saying, 'You're the lead, but we think you have a better chance here.' And I just think, 'What is this?' It's an election. That's why it's called an Oscar 'campaign.' "

Plenty of actors would love to have a career like Ruffalo's—"And I'd love them to have it," he says. In the way of advice, he offers, "I think that the important thing is to develop a voice that's essentially yours. I think that's what people respond to when they love an actor: whatever's essentially possessed by that singular person and that singular personality. It's hard today, because we're so cross-referenced and taught to be homogenized, and all the images we're fed are the same. You always hear someone is the next James Dean, the next so-and-so. And it's a trap a lot of actors fall into. So I would say to steal from the best but really work on developing your own voice and knowing who you are as an actor."

So how does Ruffalo feel about the comparisons people have made between him and Marlon Brando? "Great!" he says, laughing. "But in the end, I hope I'm singular. I hope that people say, 'That guy was completely his own thing.' It's easy to make those references, and it's tricky for a young actor, because we're so conditioned to believe we're not enough. And that thing we're so terrified of being is probably what is richest about it. Those odd inconsistencies that make you feel like an alien are the things that people celebrate in film."