Backstage on the new special, “The Muppet Show,” Sabrina Carpenter excitedly greets Miss Piggy, in whom she recognizes a kindred spirit. “I grew up watching you,” Carpenter says. “My parents grew up watching you. Their parents grew up watching——” The joke, of course, is that Carpenter ends up offending the diva by implying that she’s old. But there’s a truth to it, too: Since the madcap critters lit the lights on the comedy-variety “Muppet Show” in the 1970s, every generation has gotten its own Muppet ...The premise for “The Muppet Show” of 2026, a (for now) single-episode special premiering on...