Continuity mistake: When Radar and Hawkeye leave the 4077, the jeep they're in has its windshield in the fold-down position over the hood, but in the two shots from behind Hawkeye and Radar when they see the checkpoint up ahead and Hawkeye speeds up, the windshield has vanished and there's a star on the hood.
Visible crew/equipment: When Hawkeye removes BJ's Captain rank bars from his uniform and then pins it on Radar's knit cap, in the shot facing Hawkeye and BJ the shadow of the boom mic moves across Radar's back.
Continuity mistake: After speeding past the checkpoint Hawkeye's stopped by the MPs, and when the lieutenant takes hold of one of Hawkeye's dog tags he's holding the one on the extender chain, but next shot he's holding the other dog tag, with the extender chain and second dog tag hanging down.
Visible crew/equipment: When Hawkeye and Radar are in the jeep heading to Kimpo Air Base they drive past the checkpoint, and in their closeups the camera casts a shadow on the hood of the jeep.
Continuity mistake: In the assembly called by Major Burns at the beginning of the show, Klinger is in the front rank far left (except when the continuity error has him centre rear), but after the appearance of Hawkeye in the rickshaw Klinger isn't on parade at all.
Factual error: As Hawkeye, Radar' and BJ stop to change the flat, Hawkeye uses a scissor jack to raise the Jeep. However, the scissor jack was not in use for this model of Jeep.
Continuity mistake: In the Commander's office, Frank's arms go from being in front of MacArthur's picture frame, to gone, and back again in a matter of a few seconds.
Other mistake: In the opening, when the flags were raised, the United Nations flag is hung upside down.
Continuity mistake: When BJ, Hawkeye and Radar are being shot at, they hurry to get in the jeep. Radar gets out to get the jack, and salutes it. When the camera cuts to a shot of Radar getting back in, the jack is magically gone. It doesn't appear again.
Continuity mistake: On the way to catch Trapper, Hawkeye and Radar are stopped by an MP checkpoint. After bluffing the MP with a story about neuropraxia, the MP pumps his fist in the air saying "Move out!" The camera cuts to a wide shot and the MP is starting to pump his fist in the air again, and says "Move out!" again.
Continuity mistake: At several points, in the second half of the episode, you can see the identification number (2A401) on the general's jeep that Hawkeye stole. As well as the big star, showing it to be a general's jeep. At the end of the episode, Col. Potter shows up for the first time, in the same jeep.
Continuity mistake: When BJ arrives in Korea, he, Hawkeye and Radar are attacked by guerillas while changing a flat tire on their jeep. After installing the spare tire from the back of the jeep, Hawkeye rolls the flat tire off the to the side of the road and jumps into the jeep as Radar speeds off. Later, when they reach the camp, the spare tire has reappeared on the back of the jeep.
Continuity mistake: When Radar calls assembly, the very first shot shows some troops appearing on the parade ground. Klinger, in his straw hat, appears on parade in the front rank in the top right hand corner of the screen and stands to attention. In the next shot, however, he is seen approaching the parade ground at the double from the Post Op ward building. Next shot, he is on parade, but in the centre of the rear rank. A couple of shots later, when Major Burns addresses the troops, he is back in the front rank - screen top right. This position is confirmed later when Burns addresses him by turning his head sharp left (he is facing the parade), and Hoolihan is seen marching over to him to remove his hat.
Other mistake: It's 1952 when Potter arrives at the 4077. He tells Radar that he joined the army during WWI when he was 15 (he lied about his age). That would mean that Potter was 50 when he arrives. But he said that he'd be retiring in 18 months. Also, in the episode "Point of View" Potter states that this was the first time in 37 years that he missed calling Mildred for their anniversary. That would mean that Potter was 13 when he got married.
Character mistake: When Frank is berating Igor about the food on the trays, he calls him "Sergeant." Igor has always been a private.
Factual error: When the can of beans explodes all over Hawkeye and Hotlips, they act as though the beans are cold. In fact the beans would have been at boiling temperature as the can overheated, causing it to explode, and the two would have been burned.
Revealing mistake: When Hawkeye and Margaret turn toward the stove, and he says "Are you hungry?", watch the can. Though it is meant to look like it blew the top off, it is plain that the top was just set into the top, and a blast of air was used to blow it open. This is because of the sound, and a stream of vapor that often accompanies a blast from an air gun. A sealed can set on a heat source would have burst not only from the top, but also from the side at a seam, or the bottom. Also, they were about five feet away from the can, and the beans went up, not out at a ninety degree angle. So they wouldn't get beaned. Beans on the face were for comic effect.
The Late Captain Pierce - S4-E4
Other mistake: When Digger shows Hawkeye the copy of the death certificate, Hawkeye steps out of the shower stall and its door swings back and forth. As Hawkeye wipes his face with the towel, we can see the top of the flesh colored covering Hawkeye is wearing. (00:08:05)
Revealing mistake: When Radar carries the field phone from Col. Potter's desk over to Hawkeye who is squatting in the corner, the phone doesn't have a phone line attached. It is an EE-8 Military Field Phone, which is a wired device, not a radio - even if Radar elsewhere says he has somebody "on the radio" when in fact he is using an EE-8. (00:17:35)
Other mistake: As Burns, driving the tank, runs over the Swamp, there's no sign of the still anywhere.
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