Since the previous post went up, three separate readers of this site have written to ask, "Why wasn't Don Rickles in It's a Mad, Mad, Mad, Mad World?" In later years, Stanley Kramer would tell of how when he went to see Rickles perform, the comedian would always insult him several different ways (of course) but would especially ask, "You put every person in show business in that movie except me! Why?"
I don't know that Mr. Kramer ever gave him a direct answer but it's pretty obvious why. It's a Mad, Mad, Mad, Mad World was filmed between April 16, 1962 and December 6, 1962. Before the sixties were out, Mr. Rickles would be a pretty famous comedy star but in 1962, there were probably 300 comedians in the business who were better known than he was.