Peace on Us - S7-E2
Revealing mistake: Klinger says "The sun is going to ruin my comb-out", fingering his hair net. He has curlers under his hair net, but his hair is not around the curlers, they're just stuffed into his hair net. (00:01:10)
Peace on Us - S7-E2
Revealing mistake: When Colonel Potter's in the Swamp telling Hawkeye, BJ, and Charles that surgeons' rotation points have increased from 36 to 45 Hawkeye becomes incensed, and in these two shots from this angle we can see the edge of the Swamp set at the top, left corner of the screen.
Revealing mistake: When Hawkeye exits the tub, you can see his shorts as he wraps the towel around himself.
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)
Revealing mistake: When Hawkeye and BJ are in the showers and Margaret steals their towels and clothes, the duo head back to the Swamp naked, but we can see the top of whatever Hawkeye's wearing.
Revealing mistake: When the ambulance arrives in the compound at Christmas eve, it drives through the newly fallen snow, but it doesn't leave any tracks. Vehicles driving over a very thin snow cover always leave dark tracks, because the pressure instantly melts the snow just below the wheels. Even a person walking through the snow would leave dark footprints under these conditions.
Hot Lips Is Back in Town - S7-E19
Revealing mistake: While Hawkeye's in the shower Radar shows up with a cup of coffee, and when Hawkeye steps out of the shower stall the door swings out so we can see the top of whatever Hawkeye's wearing.
Rally 'Round the Flagg, Boys - S7-E21
Revealing mistake: When Col. Flagg holds his pistol up to stop Mr. Pak Sr. from leaving, you can see there is no magazine in the pistol.
Rally 'Round the Flagg, Boys - S7-E21
Revealing mistake: As Charles leaves the Mess Tent, you can see the camo net where there normally is none, and the background abruptly ends about 20 feet from the end of the building.
Revealing mistake: During the melee at Rosie's, after Klinger gets his money and jewelry back from the cheats a guy is thrown through windows, and though we hear the sound of smashing glass we see the shreds of plastic fluttering.
Nurse Doctor - S8-E7
Revealing mistake: While Charles is in the shower stall Hawkeye and BJ take his bottle of Vichy water, and when Charles steps out of the stall The Nurses outside the tent whistle, but we can see through the stall's openings that Charles is wearing something.
Revealing mistake: When Sherwood has died on the gurney, with Roberts holding his hand, after breathing stops, you can see the bandage on his neck still jumping in time with his pulse.
Revealing mistake: Anytime Margaret and Hawkeye are drinking in the bar, there is no liquid in the bottles.
Revealing mistake: In the supply room, as Hawkeye lights two candles, the room gets noticeably brighter. However, there's too much light for two candles, and his shadow comes from above.
Revealing mistake: In the closing scene, as the camera looks at the collected crowd, the camo net over the building poorly hides the edge of the "sky" background and the sound stage walls.
Revealing mistake: Potter is taking the driving part of the test, with Rizzo riding along. In the long shot, as well as looking at Klinger stumbling along, you can see the Jeep occupants are stunt doubles.
Where There's a Will, There's a War - S10-E16
Revealing mistake: When Hawkeye injects the adrenalin into the chest of the dying soldier at the battalion Aid Station, you can see that he is actually injecting into a piece of rubber foam soaked with prop blood. (00:13:25)
Revealing mistake: During the conversation between Potter and Klinger in the Mess tent, if you look past them you can see Margaret loitering, waiting for her cue to enter.
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