So you thought The Simpsons knew a thing or two about merchandising. Check this out: Comedy Central’s cult sensation, Mystery Science Theater 3000 (a Saturday-morning showcase for the worst B movies in history) is offering a catalog of what may be the cheesiest gift items ever devised. Along with the usual assortment of T-shirts and bumper stickers, the show’s fans — or Misties, as they prefer to call themselves — can send for an MST3K wall clock (with photocopied pictures of series characters pasted on the hands), a ”Fluid Containment Vessel” (a mug autographed by series star Joel Hodgson and his two robot sidekicks, the bubbleheaded Tom Servo and the bird-beaked Crow), and a video, Play MST for Me: The Music of Mystery Science Theater 3000, featuring clips of the show’s best musical numbers. One of the hottest-selling items has been the Demon Dog, a plastic puppy skeleton used as a prop in one of the series’ first episodes (all 20 sold out at $27.50 each). But Hodgson recently came up with a product that may do even better: ”We found a bunch of those clear plastic bubbles they use for gum machines,” he says, ”so we’re thinking about putting an MST3K sticker on them and marketing them as Tom Servo heads.” We’ll take a dozen.