Coincidentally, just days before this news, I'd seen a staged concert of a musical in which Sid Caesar was the original star in 1962 (playing 7 roles), Little Me. That was a very pleasurable experience (great score by Cy Coleman and Carolyn Leigh), but a lot of our discussion afterward was about how writing it so precisely to his comic specialties (accents, impersonations, voices, even physical shtick) makes it near-impossible to revive in a satisfying way. There's never an exact duplicate of such a performer.