Schocken Books We may receive an affiliate commission from anything you buy from this article. In his new biography, "When Caesar Was King" (published by Schocken Books), David Margolick explores how 1950s comic Sid Caesar reinvented the art of comedy in the new medium of television. Read an excerpt below, and don't miss Mo Rocca's interview with David Margolick on "CBS Sunday Morning" March 22!"When Caesar Was King" by David Margolick $29 at Amazon Prefer to listen? Audible has a 30-day free trial available right now. Try Audible for free Television was called a "medium," Fred Allen, the much-respected radio wit (and hero to Caesar and other thinking comics), once quipped, because nothing on it was well done. But Allen exempted Caesar from his broadsides. He lived around the corner from the International Theatre and would often drop by for dress rehearsals. "A casual observer might have assumed that Allen, the master, had come to instruct Caesar, the apprentice," Collier's noted.…