After 20 years of being one of the best character actors in America, on stage, screen and tube, Nathan Lane is finally a star. Until now he’s been best known for his flamboyant gay roles in plays by Terrence McNally, “The Lisbon Traviata,” in which he was brilliantly hysterical as Mendy, the Maria Callas fanatic, and “Love! Valour! Compassion!” in which he was wrenching as the HIV-positive Buzz. In 1992 he was a Tony-nominated Nathan Detroit in Jerry Zaks’s rousing revival of “Guys and Dolls.” The following year he was insanely funny as Max Prince, the Sid Caesar-ish comic in Neil Simon’s “Laughter on the 23rd Floor.” He’s made numerous movies, but his biggest screen impact came as the voice of Timon, the wisecracking meerkat in Disney’s “The Lion King.”

“For a while he was everyone’s secret genius, and now he’s the world’s secret genius,” says playwright Paul Rudnick. “When you see him you say, “Where did this man come from, and are there any more?’” The answers are: New Jersey, and no. He was born Joe Lane 40 years ago in Jersey City (he switched names at 22 after playing Nathan Detroit in a dinner-theater show). His father was a truckdriver who, he says, “essentially drank himself to death when I was 11.” Fat little Joe Lane became the class clown (“I made jokes before anyone could make jokes about me”).

On a break between rehearsals, Lane tells his story with a beguiling mixture of shyness and shtik. He acted in high-school plays, skipped college to do local theater. “The high point was this little revue called “Jerz,’ about how wonderful New Jersey was.” He became the classic struggling actor with deadbeat jobs, including bail interviewer for the police and singing telegram minstrel. “At a little Italian wedding I sang and made jokes about my acting career. They threw money at me.” He became a stand-up comic for a while, which led to a short-lived TV series, “One for the Boys,” with Mickey Rooney and Dana Carvey. His Broadway break came with George C. Scott in Noel Coward’s “Present Laughter.” Scott became a mentor, later summoning him to play Mr. Brink, the angel of death, in “On Borrowed Time.” “I told George I wasn’t right for the part, which was usually played by older British actors. He growled, “I don’t want Sir Cedric f—ing Hardwicke! When I die I want you to take me’.”

Often it was the shows that died. In the Broadway superbomb “Merlin,” starring magician Doug Henning, the intrepid Lane played with a broken leg. A better break came with Mendy in “Lisbon Traviata.” “A lot of actors didn’t want to play that role because it was so flamboyant. But I just instantly knew who that man was.” Well, sure, as a gay man, he would know, right? Lane, who could play dueling face muscles with Jim Carrey, hoists his eloquent eyebrows, flares his nostrils and corkscrews his mouth, composing a perfect line drawing that says “None-of-yer-bizness.”

He’s right. And he’s not worried about being typed as the gay guy of choice. “These are rich characters,” he says. “Albert in “Birdcage’ doesn’t even realize he’s being funny. He’s this nurturing person, easily wounded. He has a lot of dignity.”

As with all the great funnymen, there’s a melancholy bass beneath the treble of Lane’s comic persona. “Sure, I’m an Irishman,” he says. “It’s my father’s genes, his legacy.” Part of this legacy was a drinking problem that he had until three years ago. “I have a self-destructive, darker side that I deal with in therapy. But who’s gonna listen to me complain about my life now?”

Maybe not even his therapist. Lane is drenched by a shower of praise for his versatility. Robin Williams, a generous straight man to Lane in “Birdcage,” says, “We’re both laugh whores who’ll go for anything.” But in “Birdcage,” “it was like I was playing tuba with the Juilliard String Quartet. “Lane even goes for it when he’s invisible. Mike Surrey, an animator on “The Lion King,” says, “Many actors just come in and read. But Nathan would really act out the lines, even though you’re not going to see him.” Mike Nichols calls Lane “a great character actor. For that sort of range, you have to look at Alec Guinness.”

“Forum” was the first show for which Stephen Sondheim wrote both music and lyrics. “Nathan is naturally musical,” he says. In a workshop of Sondheim’s “Assassins,” Lane played Samuel Byck, who plotted killing President Nixon. Lane’s monologues were “among the best things I have ever heard,” says Sondheim. “He was playing a psychopath and he was chilling.” Sondheim praises Lane’s ability to ad-lib; director Jerry Zaks is rigging some of the numbers in “Forum” with “open measures” where Lane can improvise.

Reminded that he’s following the T. rex footprints of the great Mostel, Lane rolls his ball-bearing eyes and says, “Thanks for reminding me.” But Robin Williams says, “He’ll blow the doors off on “Forum.’ And he’ll be around for a long time.” That time includes a year that he’s committed to do “Forum,” just when he’s a hot Hollywood property. Lane appreciates the irony. “I’m always looking over my shoulder,” he says. “Mike Nichols told me, “You should allow yourself to be happy. Maybe a minute a day. Maybe three minutes next day’.” That’s enough for this mini Mostel, this bonsaied Gleason. Lane has joined the pantheon of comic actors who turn laughter into a life force.