Revealing mistake: When Hawkeye and BJ are in the showers and Margaret steals their towels and clothes, the duo head back to the Swamp naked, but we can see the top of whatever Hawkeye's wearing.
Continuity mistake: Charles arranges a prank that involves a cake. The cake looks totally different in the respective shots. At least three cakes were involved: The one Klinger gives to Margret looks different from the one she holds in her hands when walking over to Capt. Hill. The one she holds in her hand in the closeup counter shots is yet another pie.
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 ★