Continuity mistake: In the first episodes, Col. Blake's wife is named Mildred, later her name is changed to Lorraine. (In case of confusion, when Col. Potter came to the 4077th, his wife was also named Mildred, but that's not relevant).
Continuity mistake: In the first season of M*A*S*H, Hawkeye mentions that his father lives in Vermont, in the later seasons his father lives in Crab Apple Cove, Maine and has never left there in 30 years.
Continuity mistake: At one time, Col. Potter talks about how his daughter is an only child. In a different episode, he mentions that his son's wife is having a baby.
Continuity mistake: There are two sets of the 4077 compound - the outside Fox Ranch set located at Malibu Creek State Park, and the second set inside the studio's Stage 9. The layout of both sets are quite different - Studio 9's set was vastly smaller than the Ranch set, so things such as the proximity of the Swamp to the mess tent are different between the shots filmed at the Ranch and shots filmed at Studio 9, when seen within the very same episodes.
Dear Mildred - S4-E7
Continuity mistake: The injured horse that Radar, BJ, and Hawkeye go after, and who's later gifted to Colonel Potter, is played by different horses.
Continuity mistake: When Radar walks into Henry's office to tell him that there's a general there to see him, we get a good view of Henry's new desk and its beautiful ornate design, but later when Hawkeye and Trapper are carrying the desk and then it's lifted out by chopper it's a completely different desk - also note that this desk has casters.
Continuity mistake: In an early episode Hawkeye receives a sweater knitted by his sister. Subsequently in the show he has always been an only child.
Continuity mistake: In the episode "Change of Command", Potter asks Mulcahy if he "can do Methodist". In the episode "Period of Adjustment", Potter asks Mulcahy "You wouldn't lie to a Presbyterian, would you?" Just what denomination *is* Potter?
Goodbye, Farewell, and Amen - S11-E16
Continuity mistake: Early in the episode a tank is driven into the MASH compound by a wounded soldier (demolishing the latrine in the process). The tank is an M24 Chaffee dating from the mid 1940s - it is squat and angular in shape. Later on in the episode after the tank has been hidden under a tent Hawkeye decides to drive the tank into the camp dump (demolishing the new latrine on the way). The tank has changed into an M4 Sherman - it is a lot higher and more rounded in shape.
Requiem for a Lightweight - S1-E3
Continuity mistake: The bag used by Trapper for training is marked "Property of MAJ. Frank W. Burns". However, later in the series Frank's middle name is revealed to be Marion.
Henry, Please Come Home - S1-E9
Continuity mistake: As Henry is receiving his medal, Hawkeye walks up and stands close behind a man who is standing up and two women who are sitting down. The camera angle switches to show Hawkeye talking to Trapper and now they are standing behind two standing women. (00:03:55)
Continuity mistake: Radar hangs the hammer on the "Out of Order" sign and it is covering the 'of'. When he and Frank walk away the hammer has moved and is covering the 't' (00:15:20)
Continuity mistake: The psychiatrist is called Milton Freedman in this episode and Sydney Freedman in all other episodes in which he appears (always being played by the same actor - it is the same psychiatrist).
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)
White Gold - S3-E23
Continuity mistake: When Perkins is recaptured, Henry leaves his office with his cigar in his mouth. In the next shot, of him coming through the door again from the other side, his cigar is in his hand. (00:20:55)
Continuity mistake: When they are talking about taking Sophie for a walk, Roy is sitting on the bunk. His captain's bars & medical insignia are on the wrong sides. After he stands up, they are on the correct side.
Requiem for a Lightweight - S1-E3
Continuity mistake: In the first shot of Trapper running behind the jeep, he has a large patch of sweat on his chest. For the rest of the scene it is dry. (00:13:00)
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