Other mistake: In the opening, when the flags were raised, the United Nations flag is hung upside down.
The Most Unforgettable Characters - S5-E14
Other mistake: After Klinger douses himself with real gas (Potter determined that Klinger's can only had water in it, and told Radar to switch the can for real gas), and runs into the shower tent, you hear a nurse scream, and see her run out. When the door is open, there are no stalls to be seen. From all scenes shot inside the tent, you know that the stalls are big enough to be easily seen from the outside.
Other mistake: Many times during the series, soldiers are around the OR carrying a loaded weapon (magazine attached for example), when there is a sign outside the entrance that says "all weapons must be cleared before entering the building" or similar.
Suggested correction: With the rampant rule breaking seen in the show, why would this be a mistake?
Other mistake: While celebrating the ceasefire, a Jeep full of people including Father Mulcahy stops between the Swamp and the main building. There's a streamer hanging down either side of Mulcahy from above the top of frame. Unless there's a power line to the Swamp that never appears at any time, there's nothing for it to hang from.
