Factual error: When BJ and Hawkeye go to Potter to talk about Cho Lin wanting to get married at the 4077th, Potter mentions he expects to be home in Nebraska in 16 months, three weeks and four days when they try to fool Potter about Cho Lin. Potter has always said he and his family live in Missouri, however.
Factual error: Klinger says he would wear Hula Hoops(R) in his ears if it would get him a discharge. For several reasons, he is using a phrase that does not yet exist: 1) Show wise, Klinger will later try to convince Charles to invest in developing a new toy, a hoola hoop like plastic tube, being inspired by Korean children playing, and 2) plastic hoops which came to be called Hula Hoops were only introduced by Whamo in 1958. Setting episode dates is always difficult for MASH, but the Mash Olympics (inspired by the 52 Helsinki games) are still to come so we can say it must be 52. 3) The Hula Hoop trademark was only registered in 1962 to Whamo. No info. as to what name the hoops were marketed under prior to 62, but Klinger is using a term at probably ten years, at least 6 years, before it came into use. (00:04:00)
Continuity mistake: When the chopper carrying the soldier with the wounded back takes off, the sky is cloudy and, even accounting for the poor quality of the film, the weather looks very dull. The shot changes to show Radar, Hawkeye and Margaret watching the chopper leave and it is now bright sunshine. (00:44:20)
Other mistake: When Hawkeye finds the New York Times Crossword he says, "1 down, four letters..." and "1 across...four letters..." and BJ's answers are "chap" and "cast" but in the shot of the newspaper puzzle we see that both "1 down" and "1 across" are actually five letters each, not four.
Continuity mistake: After Radar calls assembly, Potter starts to address the personnel. Accounting for Hawkeye, BJ, and Margaret in Surgery, there are only thirty-three people there. In the episode "Dear Ma" (S4: Ep 17), Radar wrote that there were almost two hundred people there.
Revealing mistake: When Radar salutes Major Burns dropping the package, you can see wet spots on his uniform where he held the package. Before the bottle inside breaks, it is supposed to be dry. The crew probably re-used a single package for several takes of the shot. (00:04:45)
Revealing mistake: Klinger makes a big show of removing a big nut from the Jeep's leaf spring. The nut is clean and shiny whereas the rest of the undercarriage is painted and dirty. If you look closely, there are no screw threads where he takes it off either, there's another hex under it. The simple reason for this is that that nut doesn't belong there and never was affixed, Jamie Farr just pretended it was.
Continuity mistake: In the beginning of the episode Colonel Potter is painting a portrait of Hawkeye with his feet up, and Klinger's picture is hanging to the right of the door. But in the previous episode 'Korean surgeon' Klinger's portrait is on the left side of the door and the one of Hawkeye's is on the right side of the door, even though that portrait wasn't painted until the following episode. (00:03:15 - 00:17:55)