Continuity mistake: When Cpl. Hendrix is examined on the operating table, Klinger and Hawkeye admire his tattoos. Klinger asks "do you really think the real Louise is built like that?" and Hawkeye replies, "If she is, I'm in love". Later, when Radar talks to Hendrix, Radar says, "Her face is still pretty, and her legs are the greatest." Hendrix asks, "What about the rest of her?" and Radar replies, "There isn't any." How could Hawkeye and Klinger admire Louise's build if the tattoo was that shot up?
Factual error: Nearing the end of the show, we are told that the Chinese have become involved in the conflict and have attacked with some 300,000 soldiers. This apparently refers to massive attacks by the Chinese starting on November 1, 1950. Although the numbers are correct, the US/UN forces were unaware of the numbers. As late as November 6, the Far East Command continued to insist that there were no more than 34,500 Chinese communist soldiers in country. http://www.history.army.mil/brochures/kw-chinter/chinter.htm.
Deliberate mistake: With the show having lasted longer than the war, the producers apparently decided to turn back the clock to the very beginning of the War (June 25, 1950). To do this, it seems they have tried to make things as confusing as possible, intentionally mixing up facts, even when this openly contradicts the facts as presented in earlier episodes. For example, both B.J. and Potter arrived in or about mid 1952, but now are in the O.R. when the Chinese launch their massive offensive on 1st Nov. 1950, almost two years earlier. Trapper and Blake, who were there for the Army Navy Game which would have occurred Nov. 25 1950, are not. Many of the supporting clips also are too early or late for the events being discussed. For example, Winston Churchill's speech must have been before August 28 when the first British troops started arriving, likely also before the Canadians in July 1950, but the first MASH Unit was not set up in Korea until September 1950. Truman's speech to University of Wyoming students is actually from May 9 1950, a month and a half before the beginning of the conflict and 5 months before the first MASH was established, but the clip about his "Whistle Stop Tour" must be from the 1948 campaign. MacArthur's speech, on the other hand, is in response to the ticker tape parade of April 22 1951 when he was replaced.
Other mistake: Wendel, afraid of being shipped home, is trying to escape from the MASH by hot-wiring a Jeep. Despite just having had an appendectomy, he is leaning forward and to the right from a sitting position, which would have to put pressure directly on the incision, yet when discovered by Hawkeye, he easily and without discomfort sits up straight. Aside from him still being at the MASH, we know the surgery is recent because, just a little later, he winces and complains after making a very small movement.
Continuity mistake: After Iron Guts Kelly dies in Margaret's tent, Frank Burns visits Margaret, suspecting something. Frank asks why there is a general's star on her cot. In the ensuing 'back and forth' dialogue, Margaret's hair goes (in close ups) from nicely combed, to frazzled, back to nicely combed again (and in a different light).
Deliberate mistake: Winchester is listening on the radio to the 1951 Giants win the pennant. In the MASH series, Potter was supposed to have arrived 19 Sept. 1952, and Charles Winchester after Potter did. The Giants won the pennant during the previous year, not when Winchester was there. Also Potter, BJ and Winchester are present for New Years parties for '50-'51 and '51- '52 even though none of them arrived until late 1952.