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.
Revealing mistake: In the mess, you can see everyone has their food on metal trays and ceramic dishes. Sgt Zale, though, has his lemon pie in a polystyrene dish - so that it doesn't hurt Klinger when he gets it in the face. (00:08:15)
Audio problem: During the fight in Rosie's bar, a soldier is punched, and then thrown through the opaque window with the wood frame behind him. There is a sound of breaking glass accompanying the motion, but you can see the torn paper.
Hanky Panky - S5-E18
Continuity mistake: When Hawkeye is trying to find out whether there is anything going on between BJ and nurse Donovan, a jacket behind him disappears and the other one moves to the other side of him. (00:04:00)
Continuity mistake: While tying a tube around Margaret's arm, Pierce drops the cotton ball with alcohol on it. A moment later, it's in his hand.
The General's Practitioner - S5-E20
Continuity mistake: Near the beginning, while Col. Bidwell is watching Hawkeye operate, in the closeups he is standing by the window but in the wide shots he is standing in a different part of the O.R. (00:04:00)
The General's Practitioner - S5-E20
Visible crew/equipment: When the Colonel that Hawkeye referred to as "Bozo" is talking to General Korso on the way to the 4077th to get Hawkeye, you can see the shadow of the camera on the Colonel's lap.
Continuity mistake: While Klinger is mending the movie, the amount of film on the two reels changes a lot between shots. (00:12:20)
Factual error: Radar impersonates John Wayne, playing a scene from McLintock - a film which was not released until 1963, which was 10 years after the end of the Korean war.
Audio problem: While trying to fix the projector, Klinger says, "The bulb is hot!", but his mouth doesn't move.
Continuity mistake: After the movie breaks, Hawkeye is giving an over dramatic intro to Margaret. He has his left arm raised, and a second later, both hands are at chest level.
Other mistake: When the four nurses at the door sing, two are singing, two accompanying. The nurse on the right of the shot seems to have forgotten the words.
Continuity mistake: As Klinger waves his hands to get attention for his part, it can be seen they're empty. A second later, he has a bulb in his right hand.
Audio problem: When the bulb in the projector goes out, Klinger is trying to fix it. People throw popcorn at him, saying "Find it!" After Potter says "Hit it, Father!", watch Klinger. From the wide shot to the close up, you hear him say "The bulb is hot!", but his lips don't move.
Factual error: The MP describes the antique vase Burns is supposed to have bought as "An 800-year-old seladon vase of the Ko-Yu dynasty". Later, Burns packs up a white vase to send to his wife. Seladon is by definition green, and that kind of color glazing definitely wasn't around in the 13th century. What Burns packs up looks most like early to middle Quing period - or rather a contemporary ripoff. (00:09:00 - 00:14:00)
Visible crew/equipment: As Margaret gets into the chopper, the lighting rigs, camera and crew are reflected in the canopy.
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.
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