MAMA MARCIA: She's been a character comedienne for 30 years, but Marcia Lewis is finally getting to show a sharper edge in Chicago. "All of a sudden, I'm playing this very sexual tough cookie, and I love it," says Lewis, who's in great voice as "Mama" Morton, the shrewd and conniving prison matron. "I love sitting on the sidelines and watching the audience's reaction to the show. It's exciting every night."

The underbelly of 1920's Chicago is a long way from Rydell High School in the fifties, where Lewis presided as the principal and earned a 1994 Tony Award nomination in Grease! Rosie O'Donnell, who played Rizzo at the time, commissioned a gown for Lewis to wear to the Tonys. "The whole cast chipped in, which was so generous," she recalls. Lewis appeared on O'Donnell's talk show in January when the Chicago cast album was released. "Rosie is such a generous woman," she says fondly. "She shares her love of the theatre with everybody."

Lewis chuckles when her original profession -- nursing -- comes up. "When I arrived in New York, I walked into Mt. Sinai Hospital and got a job working nights so that I could study acting during the day. A year later, I got my union card, and I never went back." Lewis has used her skills a few times when theatre patrons became ill, and says with a wink, "I'm not sure I could hook up anybody's life support, but I give a great back rub. You never lose your bedside manner."

THE IMPORTANCE OF BEING ERIC: Some young actors view the stage merely as a stepping stone to movie stardom. For Eric Stoltz, success in films such as Grace of My Heart, Rob Roy and Little Women hasn't diminished a lifelong loyalty to the theatre.

"I don't know if 'loyal' is the correct word," says Stoltz, who spent the fall playing Algernon in the Irish Rep production of The Importance of Being Earnest and now co-stars as Baron Tuzenbach in the Roundabout's production of Three Sisters. "'Loyal' has very noble, altruistic implications, but in fact, doing theatre is an earthy, raunchy high. 'Compelled' may be the most accurate word."

The joy of tackling ensemble plays, Stoltz notes, is that "when it works, it's absolutely magical. You feel like you're in the New York Philharmonic and everyone is in perfect sync." Of Three Sisters, he adds, "If you're going to do a play that deals with spiritual, economic and emotional bankruptcy, what better time or place to do it than Times Square as the millennium approaches?"

Though Stoltz will return to movie making in the spring, he has a few dream theatre roles in mind. "I'd love to do Hamlet, Romeo the big, terrifying Shakespeare roles all appeal to me." He laughs wickedly when complimented on his less-than-ruthless approach to film stardom. "Much to the consternation of my agents, I have no vast career plan. But it could happen at any second. I could turn on a dime." -- By Kathy Henderson