Crow T. Robot, Gypsy, and Tom Servo can hold off on buying new tuxedos for the Oscars. The mechanical stars of Comedy Central's Mystery Science Theater 3000 which has made mocking very, very bad movies a national pastime were set to star in a big-screen version of their cult-hit series when Universal Pictures jettisoned the deal. "It's like getting asked to the prom," says Servo (a.k.a. Kevin Murphy), "and then at the last minute they say, 'You can't go.'" Naturally, the MST3K gang aren't taking the rebuff lying down. The show's electronic fan clubs have been writing letters of protest to Casey Silver, Universal's president of worldwide production. So far, at least 2,000 missives have been delivered. Why did the studio back out? Silver couldn't be reached for comment, and a spokesman at Universal's publicity office would only offer, "Some movies get made, some don't."