The Great Flydini, a bawdy magician, was immediately recognized by attendees of Saturday's Big Sisters of Los Angeles "Live on Saturday Night" benefit at the Hollywood Palladium. It was none other than comedian Steve Martin, who created the brief silent comedy routine in which he makes an amazing array of articles magically appear from his unzipped fly. Since quietly debuting the act during two surprise performances at the Magic Castle in Hollywood last October, Martin has attempted to establish a tongue-in-cheek mystique around his fly-by-night persona by appearing unannounced and introduced only as "the famous Italian magician, the Great Flydini." Martin's associates have been requested to keep their mouths zipped shut as to his real identity and photographers have been prohibited from snapping photos. "It's made it somewhat difficult for me to promote the show," said TV personality Sarah Purcell, chairman of the Big Sisters benefit, of Martin's anonymity. "It's a lot easier if you can say the (real) name."