Continuity mistake: When Frank inspects the local workers, the laundry woman bends down to help the kid put away the sandwich Burns suspected of being a bomb. After the cut, she's upright again. (00:10:45)
Continuity mistake: Along with Radar holding an anachronistic comic book (the Avengers), the exact issue changes between wide and close shots. One has the older Avengers logo used in the '60s and very early '70s, while the second issue Radar is holding has the newer Avengers logo that just gained currency as the episode was being filmed. (00:00:45)
Continuity mistake: Early in the episode it is stated that Margaret's tent door is padlocked while she is in Tokyo. But when she gets back, she just walks straight in. (00:22:20)
Continuity mistake: When Jack delivers the patient to the MASH and when he is taking photos of the operation, there is no wound on his right hand. It only appears when Col.Potter says that he treated it "months ago". (00:04:30)
Continuity mistake: After Jack wins a drink from Hawkeye and BJ, Hawkeye grabs the orange to inspect it for tears to prove his magnet theory. After the angle change, he grabs it again.
Continuity mistake: When Carly is talking about Hawkeye being a "mortician's delight", she is gesturing with her right hand, and it's about waist height at the end of the motion. When the camera goes to a wide shot, her hand is up by her chin, about eight inches from her face.
Continuity mistake: As the interviewer talks to Hawkeye, his hand alternates from just below the microphone head to just above the bottom end between angles.
Answer: The C-42 was a military variant of the Douglas DC-2. Very few C-42's were built, so it's questionable that Potter would specifically have seen that particular model, but, given his military background, it's not entirely unreasonable that he might use the military designation even when the aircraft in question is actually a civilian DC-2.
Tailkinker ★