What is sin City's most popular parlor game? Speculating on what will replace the Mirage's Siegfried & Roy spectacle: a vacant showroom on the Strip is like undeveloped waterfront property in Miami. After a grace period--an onstage tiger attack Oct. 3 all but ended Roy Horn's career--promoters are flooding parent company MGM Mirage's offices with proposals ranging from a production of "Hairspray" to various Celine-style endeavors. NEWSWEEK has learned that Cirque du Soleil, the human circus troupe that already has three Vegas shows and is opening a fourth this summer, has held meetings to think about a fifth. With Cirque's Vegas track record, that makes sense. But what's puzzling--if not creepy--is why huge Siegfried & Roy marquees still loom around town. Alan Feldman, an MGM Mirage spokesman, says the duo remains a part of the resort's identity. A zoo with their animals is still open, and a cartoon, "Father of the Pride," airs on NBC this fall. Creepier still is the centerfold in the 2004 Siegfried & Roy calendar: a 20- by 24-inch poster of Montecore, the mauler. Feldman says, "If someone wants to be cynical or sarcastic, that's something someone would smirk about."