Continuity mistake: When Radar is slipping the glass of milk into Buzz's tent, we see the outside of the tent and there are no windows. From the inside, the milk is placed on a table that is right under a window. Also, the milk is already on the table in a scene before Radar puts it there. (00:13:20)
Factual error: When Radar, Hawkeye, and BJ find the letter from cpl. Benson to I Corps, Radar says that cpl. Benson's been here since June. Later in the episode when col. Potter, Radar, Hawkeye and BJ confront Benson, Benson says he is there on orders of a colonel who did not get treated quickly enough. Potter says he remembers this colonel was there a couple of months back. BUT, this episode of M*A*S*H takes place during Kentucky Derby Day. The Kentucky Derby has always been held the first Saturday in May. So, if Benson has only been at the 4077th for two months, and he arrived in June, then this episode should be taking place in August, not May.
Factual error: While watching the Sonja Henie movie "Sun Valley Serenade" Colonel Potter says at one point of the movie "This is supposed to be where she does a triple axel and ends up in a split." Then he has to leave and says "Now I'll never get to see it." He wouldn't be able to see it until 1989 when Midori Ito from Japan was the first woman to complete a triple axel in competition, Tonya Harding was the 2nd woman to complete one and the only American woman. And I doubt Sonja Henie ever did anything as complicated as a triple axel even with her 3 Olympic Gold Medals.Sonja Marie
Deliberate mistake: These errors I assume were caused by the show running 3 times longer than the real war. Col. Potter arrived at MASH in September 1952 a year before the war ended, then a few months passed by Margaret got engaged for 8 months, then Frank Burns left and Charles took his place. In this time the war would have ended. In the final episode Margaret mentions Charles has been there for 2 years. Which means he would have arrived in 1951 a year before Trapper and Henry left and Col. Potter arrived. It's a lot to take in.
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.