According to 'Get Smart' writer-producer Leonard Stern, the idea of a "nude bomb" was forced on the writers by the producers. The original idea by the writers - who also wrote the original series - was for the villain to want to control the world by dressing everyone in his designer clothes. The film was supposed to be titled 'The Return of Maxwell Smart' but the producers thought the new title would draw more viewers. Because of many disagreements, the writers were not allowed on the set.
According to Barbara Feldon, she was not asked to reprise her role of 99, but wouldn't have accepted even if she had been.
Around the time of the release of Max la Menace (2008), 'Get Smart' co-creator Mel Brooks commented that he wasn't consulted for any input at all by the production of Le plus secret des agents secrets (1980).
Only one of the lead cast from the original TV series appeared in this movie. This was main character and actor, Don Adams as Maxwell Smart. Neither Barbara Feldon as Agent 99 nor Edward Platt as The Chief appear, Feldon apparently wasn't asked but did end up appearing in the later 'Get Smart' tele-movie Le retour de Max La Menace (1989) whilst Platt sadly had passed away about five years earlier in 1974. Supporting actor Robert Karvelas as Larrabee was the only other original Max la menace (1965) cast member to appear in this movie. A character called the Chief did appear in this movie and was played by Dana Elcar.
Don Adams admitted he only did the movie for the money, because his wife at the time, Judy Luciano was pregnant. In reality, he hated the script.
Joey Forman: The actor who played Hawaiian detective Harry Hoo from the original Max la menace (1965) TV series plays Agent 13.
Bill Dana: As Jonathan Levinson Seigle, a character name which is a parody of Jonathan Livingston Seagull from Jonathan Livingston goéland (1973).