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.
Requiem for a Lightweight - S1-E3
Audio problem: When Margie is saying she is impressed, Trapper replies "I should hope so", but his mouth doesn't move.
Revealing mistake: When the second shell explodes outside, the shelf in the right foreground shakes a moment, then the top suddenly flips up, dumping the bottles that were on it. Obviously a stagehand flipped it when no bottles fell.
Continuity mistake: In the mess tent, Hawkeye is attempting to get the reporter to focus on BJ instead of him by telling the guy about the defibrillator made by BJ to save a life in the O.R. As Hawkeye is making his point, the reporter is putting a sheet of paper into a folder on his typewriter case. After the camera cuts to a close up of the reporter saying his next line, he's putting the paper into the folder again.
Comrades in Arms: Part 2 - S6-E13
Audio problem: When Hawkeye and Margaret are being driven into camp, everybody is cheering. Watch the driver of the jeep. He hits the horn button a number of times, but the horn is never heard.
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)
As You Were - S2-E20
Character mistake: When Hawkeye asks Frank what he is doing, Frank replies he is lining up all bottles and jars "according to height and popularity". In fact, the bottles are not lined up according to height at all, also the order of condiments is different on the two tables. The sweet and sour gherkins Frank mentions are not there at all - during the pan shots you can see the line ends with the pepper. (00:01:50)
Factual error: Charles mistakenly injects a Post Op patient with curare instead of morphine. This would have been hard to do. Curare was not approved for use in Korea by the U.S. Army and it would not have been there. Even if it had been, curare was used in conjunction with anesthetics in the operating theatre. It would make no sense to have it in the Post Op. (source pg. 14 "Notable Names in Anasthesia" by J. Roger Maltby, Royal Society of Medicine - Great Britain). (00:12:20)
Continuity mistake: When Hawkeye hits on the nurse after Charlie's first flyover, his beach chair instantly folds itself up. (00:06:40)
Continuity mistake: In the assembly called by Major Burns at the beginning of the show, Klinger is in the front rank far left (except when the continuity error has him centre rear), but after the appearance of Hawkeye in the rickshaw Klinger isn't on parade at all.
Continuity mistake: After Klinger's file cabinet gets bombed, BJ appears in the window. He's facing directly ahead, head slightly tilted to the right. When the camera goes to a close up, he's in quarter profile, left cheek forward. In the long shot, he's back to the original position.
Revealing mistake: A number of times, during the night periods (for instance, during an OR scene) the windows are dark when the lights are on in the room. Then when the lights go out, the windows brighten up. They, and the interior lights seem to alternate lightening and darkening.
Revealing mistake: In the first scene, when the camera pans back, in the upper left corner of the screen you can see that a part of the tent has been removed to make room for the camera. (00:02:15)
The Sniper - S2-E10
Revealing mistake: When The Sniper begins his attack, a sandlot football game is in progress in the compound. As the quarterback goes back to throw a pass, he waits just long enough for the ball to be "shot" out of his hand.
Plot hole: In a tape home, Winchester implores his father to get him out of the MASH and suggests that Senator Griswold should help as his father "paid good money for him". As the length of time the show ran so exceeds the length of the war itself, inconsistencies for dates are perhaps unavoidable, and it might not be fair to call them mistakes. In this case however, the writers/producers have carelessly picked a senator who only served from November 1952, making dating inescapable. As Charles, in the same episode, complains how hot it is and everyone is in shirtsleeves, it must be very late spring, perhaps May, at best, just a month before the end of the war. To emphasize the mistake, by the next episode it is late fall/early winter. (00:12:45)
Continuity mistake: After Hawkeye and Trapper cut the bomb wires, Trapper kneels down to see if it's still ticking, and his hand disappears from his helmet. (00:23:05)
The Sniper - S2-E10
Continuity mistake: When Hawkeye is preparing to go for his picnic, Radar brings him some brandy from Col. Blake. There is only a small amount of brandy in the bottle, which is commented on. Radar takes a jug of martini from the still to top up the bottle, but this is not done and the jug of martini remains on top of the stove untouched. When the picnic scene takes place, the brandy bottle is now nearly full with the brandy/martini mix. (00:10:00)
Character mistake: In the opening scene, Hawkeye and Trapper are operating on a two-star general. But neither one of them or the nurse is wearing their masks. They are under their chins.
Answer: Even an Army field hospital would have SOME weapons for self-defense if the enemy attacked. What's meant is that it's not a combat outfit, and therefore wouldn't have enough weapons to actually attack anyone. (It's also mentioned a few times that the Officer of the Watch is supposed to carry a pistol at all times, but Hawkeye refuses to do it when he's in charge and Colonels Blake and Potter don't enforce the rule).
Captain Defenestrator