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 and Chico appeared less prominently. The two younger brothers, Gummo and Zeppo, never developed their stage characters to the same extent as the elder three. They each left the act to pursue business careers at which they were successful, and for a time ran a large theatrical agency through which they represented their brothers and others. Gummo was not in any of the movies; Zeppo appeared in the first five films in relatively straight (non-comedic) roles. The performing lives of the brothers owed much to their mother Minnie Marx, who acted as their manager until her death in 1929. The