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.
About Duncan[]
Duncan is Winchester's patient and he is recovering in post-op after an operation but the MASH has run out of morphine painkillers. So the MASH staff devise some sugar pill placebos to give to them. Winchester gives a placebo to Duncan who asks how long it would take to work. Winchester, who is not very convinced about the use of the placebo in the first place starts to mumble something unconvincing about it depending on the metabolism, rate of ingestion.... Fortunately Margaret steps in and says definitively: "Ten minutes."
We do not know if the placebo worked for Duncan - certainly Winchester administered it a lot less convincingly than Hawkeye with Private Collins or Potter with Private Rifkin. Potter later says the placebo worked for almost half the cases. Perhaps Winchester's patient was in the other half?
Duncan's rank is not given or mentioned nor is he ever seen in uniform, but in the M*A*S*H series it is a common practice to give ranks to Corporals and Sergeants in the billings and list Privates simply by their last names, so it is deduced that Duncan is a private.
Duncan might be a marine. In the opening scene of the episode, in the O.R. while operating on the soldiers Potter mentions that the marines may be good fighter but are lousy drivers. According to Hawkeye, their troop truck went over a cliff, leading to many of the patients having broken bones. They were, it seems, returning from the front after a battle when the accident happened.