(newly rewritten for 2012)
In 1991, he followed it up with Claymation Comedy of Horrors, a thirty-minute piece starring Wilshire Pig and Sheldon Snail, a couple of original creations the studio developed (perhaps in order to launch a multi-media property of their own to go with their successful avertising characters). Wilshire was conceived as a a gruff, hustling pig not unlike a swine version of Rotten, the trashy guy from Witch's Night Out. In the special, he and Sheldon find a map to Dr. Frankenswine's lab and spend half an hour poking around the castle, building to a climax in which a giant monster goes stomping around the countryside smashing sheep to the strains of "Climb Every Mountain." Though it was obviously conceived as a Halloween special, it was originally aired in May, 1991.
So, where did this one go wrong? Why didn't this one become even a cult hit? The most obvious answer is that they didn't air it as much as some of the others, but that's not really accurate - the Disney channel aired it as a Halloween special throughout the 1990s. The biggest problem is the script - while there are some terrific sequences here, it suffers from a less-than-engaging plot and a general sense that they're just not getting the timing or the pacing right for the jokes to work. It didn't make me want to go watch their Easter special from a couple of years later. Perhaps they should have followed the template of the beloved Christmas special and just done a series of Halloweenish musical numbers, but I get the idea not only that they wanted to try to get Wilshire and Sheldon off the ground, but that they wanted to use some ideas they'd been sitting on; on the Will Vinton web page there's some animation art for an aborted Frankenswine project that was in development from 1979-82.
This gets removed from youtube when it's posted, prompting the usual whining from people who think that putting up an "I don't own this note" should somehow trump copyright protection (I'm always amazed at how many people think I should be fighting the evil studios for the right to put up free download links to the cartoons they make). It's available on DVD in a collection with the Christmas and easter specials. The glowing reviews on amazon almost universally cover only the Christmas entry.