Gumby, the little green plasticine boy from the toy-land world of Gumbasia, first burst onto TV screens on the Howdy Doody show in 1956. By 1957 the landmark children's show had launched its own series of reality-bending adventures. Gumby could walk into storybooks and through mirrors, blast off to the moon and travel back to the dinosaur age, and roll himself into any shape he chose. What kid …