Maybe it’s his introspective intensity. Maybe it’s his own recent departure from the realm of the underaged. Or maybe Robert Sean Leonard, who turns 22 this month, is so impressive playing misunderstood teenagers because he doesn’t see such roles as others see them. As Douglas Bridge, the withdrawn but dutiful son in Mr. and Mrs. Bridge, Leonard sprouts from Eagle Scout into World War II fighter pilot and manages to dismay his parents (played by Paul Newman and Joanne Woodward) every step of the way. ”Douglas was a real rebel and fascinated bu anything that he wasn’t supposed to do,” says Leonard, who plays the young suicide, Neil Perry, in Dead Poet’s Society. He was convinced Douglas wasn’t destined to relive his father’s stifled existence, but there he was disappointed. ”I couldn’t believe I turned out to be a lawyer,” Leonard says. ”I mean, I just assumed I would have become a writer Evan Connell (whose novels were the film’s basis).” That passionate naïveté was what the filmmakers were looking for from the young actor. Producer Ismail Merchant says that a big factor in his choice was ”the honesty and sincerity I found in his face.” Capping his definitively agonized adolescents, Leonard has just finished a run as the ultimate misunderstood teen in a New York Stage production of Romeo and Juliet, but now he may be moving on to slightly more mature roles: He’ll appear as a newlywed this summer in the comedy Married to It.