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)
Continuity mistake: In the episode 'Chief Surgeon Who' (season one), near the end of the episode we see Radar in Col. Blake's office smoking a cigar with ease, but in the first episode of season six when Col. Potter offers Radar a cigar, he doesn't know how to smoke it and he throws up after he puffs it.
Continuity mistake: When Charles first arrives at the 4077, his scarf changes from shot to shot. It is tucked in neatly, then loose, then tucked in again.
Continuity mistake: When Colonel Potter, BJ, Hawkeye, and Charles are in the changing room, Charles wants to be alone so he takes his tan jacket off the first nail on the right and leaves, but in BJ and Hawkeye's closeups the tan jacket is still hanging on that first nail, then it vanishes again.
Continuity mistake: Charles and the G.I. lay waiting for an explosion. When the last mortar hits, the explosion is just to the left of the back tire, the jeep is untouched. After a cut, the jeep is trashed and burning.
Fallen Idol - S6-E2
Continuity mistake: Look at the stains on Winchester's clothes in the O.R. sessions. Both times the stains match. There would be different stains because of the cleaning process.
Last Laugh - S6-E3
Character mistake: BJ refers to his friend Leo as colonel. He's wearing two silver bars, insignia of a captain.
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: While Colonel Potter is painting the portrait of Charles, the portable military field desks behind Potter are all open - note the front doors are flipped down, but in the closeup of Charles holding the painting of himself the doors are folded up. And the books, etc. atop the field desks change as well.
Revealing mistake: While painting Winchester's portrait, the camera looks across Potter's position. As it does, the picture is totally finished, though Potter acts like he's working on it.
Continuity mistake: While Charles is reading the letter about his nephew being discharged because of fainting spells, Klinger feigns a fainting spell falling forward onto Hawkeye's cot, and his body lies lopsided with his leg hanging off, but when it cuts to the next shot Klinger's perfectly positioned on the cot. Also, note the mail Klinger tossed earlier onto Hawkeye's cot, near his pillow, is now neatly tucked under the blanket towards the foot of the cot.
Continuity mistake: In the last O.R. of the episode, Winchester is wearing a surgical gown with the same blood stain pattern as in the previous episode. This also would be impossible given the cleaning procedures.
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)
Change Day - S6-E8
Continuity mistake: From the back, while denying Charles entry, the whistle Klinger has on flips over his left shoulder. A moment later, as Hawkeye and BJ walk up, the whistle is in front.
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? (00:01:10 - 00:07:20)
Other mistake: In the episode where Radar is talking to Corporal Hendrix, Radar says that he was thinking about getting a tattoo himself. But in season 3 episode 7 when Col. Blake was giving Radar his physical he had an anchor on his right arm which he said was his new tattoo. (00:08:20)
Visible crew/equipment: When Colonel Potter surprises everybody with his "little Olympics" idea in the mess tent, after Margaret comments, "I just know I'm not going to have anything left for Donald," at the start of the next shot the boom mic casts a very quick moving shadow on BJ.
Visible crew/equipment: While Colonel Potter has everyone gathered in the mess tent to surprise them with his "little Olympics" idea, the studio soundstage is visible at the top, left side of the screen.
Other mistake: When Penobscot is approaching the group, you can make out "4077 USA MASH" on the bumper, even though the the numbers and MASH are partially obscured.
Continuity mistake: As Ames is pitched the idea of diet and exercise, he has his fork up with a bite of egg on it. When Hawkeye reaches for the fork, it's upside down and clean.