Factual error: Another premature mention of Godzilla when Col. Blake announces that night's movie, "Godzilla and the Bobby Soxer". (00:01:57)
Revealing mistake: As Hawkeye calls for quiet in the officers' club, Henry pulls the tonearm off the record player, it comes away trailing a long wire behind it. Why would it even have a long wire to trail? After all, wire costs money too. It's not like the tonearm is designed to come off and be used remotely. My guess is: they lengthened it, so the shot could be taken several times without repairing the record player every time. Now, WHY they would do it that way and not simply use a dud record player is beyond me. (00:20:55)
Visible crew/equipment: When Margaret's in her tent reading just as Hawkeye walks in to give her the physical, the chalk T-mark can be seen on the floor.
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