The new Disney+ documentary “Jim Henson Idea Man” conjures the life and mind of the visionary who created the Muppets and changed not only an art form, but also the parameters of storytelling.

W ith the new Muppet movie now in theaters comes a new Muppet — the star of the show, named Walter. We have yet to personally meet him; what with his busy press schedule, he hasn’t found time to sit ...