Marx Brothers made a guest appearance to introduce the "Tonight Show's" new host, Johnny Carson. Around 1960, the acclaimed director Billy Wilder considered writing and directing a new Marx Brothers film. Tentatively titled "A Day at the U.N.", it was to be a comedy of international intrigue set around the United Nations building in New York. Wilder had discussions with Groucho and Gummo, but the project was put on hold because of Harpo's ill-health and abandoned when Chico died in 1961. He was 74. Three years later, on September 28, 1964, Harpo died at the age of 75 of a heart attack
Marx Brothers one day after heart surgery. In 1966 Filmation produced a pilot for a Marx Brothers cartoon. Groucho's voice was supplied by Pat Harrington Jr. and other voices were done by Ted Knight and Joe Besser. In 1970, the four Marx Brothers had a brief reunion of sorts in the animated ABC television special "The Mad, Mad, Mad Comedians", produced by Rankin-Bass animation (of "Rudolph the Red-Nosed Reindeer" fame). The special featured animated reworkings of various famous comedians' acts, including W. C. Fields, Jack Benny, George Burns, Henny Youngman, the Smothers Brothers, Flip Wilson, Phyllis Diller, Jack E. Leonard, George Jessel