Sometimes You Hear the Bullet - S1-E17
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: Charles enters Col. Potter's quarters while Potter is sleeping. Potter sits up in bed while Charles whines and complains about his sister's engagement. In all the shots facing Potter, the hair at the top of his head is very messy and pointing up. In every shot facing Charles, Potter's hair is normal.
Visible crew/equipment: As Hawkeye is first approaching Danker during the triage scene, a boom mic can be seen at the top of the screen.
Springtime - S3-E6
Other mistake: While Radar is measuring the camp, he says that last year they had 2,986 square feet, but this year they have 2,863 square feet. The square root of 2,863 is about 53.5, so unless the camp is 53 feet by 53 feet (!) his numbers are WAY off. (00:16:15)
Visible crew/equipment: After Radar shows the box of bees to BJ and Hawkeye, when BJ gets in the jeep and drives off, just before the shot cuts away we can see the T-mark on the ground at Radar's feet.
Factual error: Throughout the series, actors are seen wearing cuffless permapress fatigues. Neither cuffless nor permapress utilities were available until the 1970s.
Continuity mistake: First, Radar is seen drumming on his tin cans with bare hands. After cut, when the hula girl appears, without interruption of the drum pattern, he suddenly is holding some sort of drumsticks. (00:15:00)
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.
Continuity mistake: During the shelling on the road, BJ gets very muddy. When they get to the bar, he is much cleaner - e.g. all the mud has disappeared from his right arm. (00:44:30)
Aid Station - S3-E19
Factual error: Mulcahy asks Hawkeye if he trusts God. Hawkeye replies "It says I should on all of my money." However, the phrase "IN GOD WE TRUST" didn't appear on American bills until 1957.
Good-Bye Radar: Part 2 - S8-E5
Other mistake: When Potter enters the Swamp, his rank insignia is placed wrongly, with the feet of the eagle pointing to the front of the collar. The feet should point toward the shoulder side of the collar, as they are the next time we see Potter.
Continuity mistake: In the office, Radar is getting ready for bed, and has taken off his shirt. When he goes to tuck in his Teddy, he suddenly has sleeves.
Factual error: When the South Korean Colonel and General are in the mess tent, their rank insignia are wrong. The insignia they are wearing are for the U.S. Army.
Suggested correction: They could have been Korean Augmentation To the United States Army (KATUSA) officers, who were Koreans drafted or volunteered into the US military to act as a liaison between Koreans and the US military. As such they wore US uniforms and rank.
Audio problem: The original "gin machine" is entirely metal, but when Frank throws it on the floor, you hear porcelain breaking.
Visible crew/equipment: After Potter tells Klinger that his lawyer, Schaeffer, is a fake who's impersonated a chaplain among other things, when Schaeffer tells them that 25 couples are living in sin, in the next shot two curved chalk actor's marks can be seen on the floor. (00:35:45)
Goodbye, Farewell, and Amen - S11-E16
Continuity mistake: When the injured tank driver appears in the open hatch while Margaret's yelling at him, he does not have a bushy mustache, but in the next shot in the OR we hear Margaret telling Potter about the tank driver while they're operating on him, and when the camera pulls in closer we see that he has a big bushy mustache. (00:10:50)
Goodbye, Farewell, and Amen - S11-E16
Continuity mistake: While everyone's gathered for their last evening together, taking turns telling what their life will be like when they get home, there are three closeups of Kellye in which we see that her caduceus insignia pin is on her right lapel and her First Lieutenant bar is on her left lapel, though it should be the opposite way, and her closeups are not flipped. The pins are on the proper side in other shots of Kellye during the episode.
Goodbye, Farewell, and Amen - S11-E16
Visible crew/equipment: While Klinger is on the phone trying to set up BJ's transportation home, just as Winchester walks into the office pointing out the company clerk the shadow of the moving boom can be seen on the wall, and it's also visible when Winchester takes the mailbag and dumps the contents. (00:42:50)
Goodbye, Farewell, and Amen - S11-E16
Continuity mistake: After Klinger presses Potter about getting rid of the tank Potter tells Klinger to act like a sergeant, and in the shot from Potter's office Klinger walks out with both of his helmet straps hanging loose, but when it cuts to him walking into the outer office one of the straps is suddenly gone. (00:33:45)