Something's gone awry when Saturday Night Live's purest persona, Ana Gasteyer, is trading impressions of Celine Dion for pelvic thrusts, wicked violin solos and orgasmic highs in Broadway's The Rocky Horror Show. What led her to commit such Madonna-esque debauchery onstage?

"They offered," laughs Gasteyer — a Rocky castmember as kooky Columbia until August 19, when she'll take a break before returning to SNL. Unfortunately, the actress — who was "taken with the concept of being a groupie" — found that not even carousing with gender-bending aliens and a dolled-up Luke Perry could spare her a hazing from Rocky's hecklers.

"One time," Gasteyer recalls, "somebody yelled, 'Go back to SNL!' — but I incorporated a slam at this guy in Columbia's tirade." Still, while the funnylady easily blows off such nonsense, she acknowledges that Perry (who plays prudish hunk Brad) has taken it much harder. "People can be really mean to Luke [because of his past on Beverly Hills, 90210]," she sighs. "I have no patience for that."

Of course, raucous audience participation isn't Rocky's only controversy: What's the story behind rocker Joan Jett's alleged temper tantrum prior to quitting and leaving Columbia's portrayal to Gasteyer? "That was more of the press," Gasteyer responds. "Joan actually called me my opening night to wish me luck."

Her romp through "Transsexual Transylvania" will be fondly remembered by Gasteyer, whose SNL sketches never include anything like the risqu&#233 goings-on at Dr. Frank-N-Furter's mansion. "I only got to make out in [my] first season, when I was still new meat," she laughs, adding that like her beloved Margaret Jo character, she's been relegated to talking "Delicious Dish" instead of being one.