Continuity mistake: When Klinger is coming over the hill at the end of the episode, the camera shows him in the outdoor setting, and the spot he's on has sparse vegetation. When the camera goes to a close up of him, the trees and shrubs are thicker and closer to him. This alternates a couple of times.
Other mistake: When Trapper and Hawkeye make the right turn after Trapper tries to use the restroom, you see that Trapper avoids the left side of the road just after the turn. This is to avoid the explosive charge set in the ground used to simulate a mortar round exploding.
Continuity mistake: After Klinger's file cabinet gets bombed, BJ appears in the window. He's facing directly ahead, head slightly tilted to the right. When the camera goes to a close up, he's in quarter profile, left cheek forward. In the long shot, he's back to the original position.
Continuity mistake: In the mess tent, Hawkeye is attempting to get the reporter to focus on BJ instead of him by telling the guy about the defibrillator made by BJ to save a life in the O.R. As Hawkeye is making his point, the reporter is putting a sheet of paper into a folder on his typewriter case. After the camera cuts to a close up of the reporter saying his next line, he's putting the paper into the folder again.
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.
Revealing mistake: Toward the end of the episode, Henry is talking to a general on the phone when the chopper is coming in. He's trying to tell the man that he can't hear him. As he continues trying to talk, he gives up, and hangs the receiver up on the skeleton's head. If you look, you can see the hook that was conveniently placed for the gag.
Plot hole: When the truck with the orphans arrives, Col. Potter and Nurse Cratty greet each other like one would an old friend. Being new to Korea, Col. Potter doesn't know Nurse Cratty - as becomes clear from his reaction to Hawkeye's explanation to BJ earlier (who doesn't know Nurse Cratty for the same reason, but that's not relevant for this mistake). Note that in other parts of the series Col. Potter is depicted mostly as somewhat old-fashioned and reserved towards strangers.