Private Duncan was a U.S. Army or U.S. Marines private who made a single appearance in the Season 6 episode of the CBS-TV series M*A*S*H titled "Major Topper". The part of Duncan was played by John Kirby who would later become a noted Hollywood acting coach. John Kirby is also the son of M*A*S*H actors Bruce Kirby who played Sergeant Kimble and also brother of Bruno Kirby who played Private Lorenzo Boone.