The Groundbreakers: Film

In “Iron Man,” he is the wily badass superhero Tony Stark — a pillaging, evil, destructive arms dealer whom women want to cuddle.

In the Hollywood sendup “Tropic Thunder,” he is the egomaniacal blue-eyed Aussie Kirk Lazarus, a stereotypical thesp so dedicated to his craft that he undergoes skin pigmentation to turn himself black.

And in the upcoming drama “The Soloist,” he is L.A. Times columnist Steve Lopez, the empathetic guy who befriends a schizophrenic Skid Row musician.

Ask Robert Downey Jr. about his recent successes and you’ll get a classic Downeyesque response: “I can’t say it has any real meaning, but it’s more encouraging than the other options.” 

“Iron Man” director Jon Favreau gets a huge chunk of kudos and gratitude from his star. “If there was anything groundbreaking about me lately, it’s that Jon started a bit of a trend. He makes less-than-obvious casting choices for big movies. He motivates people who had been around for a while and lets ‘em take a shot at the title.”

Downey is well known for his “Robertisms” — those moments of razor sharp wit and lightening-like improvs – most recently seen on the set of “Iron Man.”

“He did a lot of changing,” says screenwriter Mark Fergus. “You’re on the Downey roller coaster just hanging on for dear life. You’re just watching, listening and throwing things at him. And he’s firing things back at you. He’s been called a John Coltrane kind of actor. He’ll take a melody and rip it to shreds and put it back together and reassemble it and flip it. If you want to take that ride with him, it’s going to go to some very exciting places, but you can’t be precious about the scene.”

The actor’s current project is Guy Ritchie’s new film, “Sherlock Holmes,” and as one would expect, this Holmes is not your grandparents’ sleuth. Downey’s Sherlock is a lean, mean, fighting machine. He took a cue from his actor friend Chris Martin, an avid Sherlock Holmes fan, who told him, “You’ve got to be gaunt. And I mean kind of wildly gaunt.”

Playing “the left brainiac Sherlock” is the latest in a series of iconic characters that Downey has taken on, starting with Charlie Chaplin in 1992.

“It’s a huge risk to play someone that so many people have an idea about,” Downey says. “You just have to have the humility to roll your sleeves up and go, ‘All right, let’s dive in.’ When I was doing Chaplin, the more I researched him, the less capable I felt of stepping on a set and doing it. Then you reach a critical mass and, all of sudden, you’re out there. And, like it or not, I’m going to be associated with Sherlock Holmes by next November.”

“Sherlock Holmes” wraps in January, just in time for Downey Jr. to put on his “Iron Man 2″ power suit in March.

Follow @Variety on Twitter for breaking news, reviews and more