I think Rizzo’s a less evolved form of Xena,” says Lucy Lawless, who, while on hiatus from her role as TV’s tough-talking, leather-clad butt kicker, is playing the tough-talking, leather-clad vixen in Broadway’s Grease! Lawless landed the role after one of the show’s producers caught her impromptu rendition of ”I’m an Old Cowhand” on The Rosie O’Donnell Show. ”Lucy brings with her an aura,” says Grease! producer Barry Weissler. ”Before she even walks on stage, we’re already wondering what the Warrior Princess is going to act like as Rizzo.” One-upping her predecessors (including O’Donnell and Brooke Shields), Lawless adds sexuality and menace to the role, slaying audiences — made up largely of Xenaphiles — like so many rampaging Visigoths. Allowing EW a glimpse of her backstage lair, the New Zealander, who’ll be going medieval on Sandra Dee through Oct. 19, discusses her battle plan for the Great White Way.