Trivia: The only member of the cast to have actually served in the Home Guard was John Laurie. Arthur Lowe, John Le Mesurier, Clive Dunn and Arnold Ridley were in the regular army.
Trivia: Danno was played by Tim O'Kelley in the 5-0 pilot. But a NY test audience told CBS they didn't buy him as a serious cop because he was too much of a "smart-cracking, Jimmy-Olsen-type gee-whiz kid." Leonard Freeman took the criticism to heart, and recast the part with James MacArthur for the series.
