For Eric Jacobson, playing a glamorous pig has been the role of a lifetime. In recent decades, he has become the lead voice and puppeteer behind several instantly recognizable Muppets, among them Bert, Grover and Oscar the Grouch on “Sesame Street” and Fozzie Bear. But when it comes to aura and cultural significance, he said in a recent phone interview, “Miss Piggy’s on another magnitude, as she would tell you herself.”