ALL COMEDY IS CONSERVATIVE:

Focusing less on prepared material and more on interaction with his audience, he had found his voice. He was not the first insult comedian -- and in fact an earlier master of the comic insult, Jack E. Leonard, was known to complain that Mr. Rickles's act was too similar to his -- but he soon became far and away the most successful.

Bookings in the late 1950s at the Slate Brothers nightclub in Hollywood and the lounge of the Sahara Hotel in Las Vegas spread the word. During his Slate Brothers engagement, Carl Reiner recalled in "Mr. Warmth," the biggest names in show business felt that "if they hadn't been insulted by Rickles, they weren't with it."

His appearances insulting celebrities on the Dean Martin roasts and his sparring matches with Carson cemented Mr. Rickles's reputation, but his unscripted brand of humor proved an uneasy fit for weekly television. A variety show in 1968 and a situation comedy in 1972, both called "The Don Rickles Show," were short-lived, as was "Daddy Dearest," a 1993 sitcom in which he and the comedian Richard Lewis played father and son. The closest thing to a hit show he had was "CPO Sharkey," a Navy comedy, which aired from 1976 to 1978.

Critics were often not sure what to make of Mr. Rickles. John J. O'Connor of The Times wrote in 1972 that for some his humor "will always remain tasteless," while for others "it has its delicious moments of madness." Tom Shales of The Washington Post, 26 years later, was more enthusiastic, praising him as "mythic, timeless, fearless -- endowed by the gods with some absurd miraculous gift."

No critic, however thoughtful, could quite explain Mr. Rickles's durability in show business, given that until the end of his career he was peppering his act with slurs and stereotypes long out of favor. And yet he not only got away with it, but he also flourished.

Tweet   @brothersjudd