The Silent Movie Theater ran a fantastic showcase of Jim Henson rarities on Tuesday night. Before “The Muppet Show” and “Sesame Street,” Henson spent two decades working in commercials, introducing Muppet characters that would become household names later on. Henson’s commercials are full of an irreverent humor that feels far ahead of its time, routinely mocking the medium’s peculiar conventions and getting away with murder behind the guise of his universally lovable puppets.