Factual error: In this episode, the regulars receive and respond to letters from a Fourth-Grade class in Hawkeye's home town. Charles receives one from a little girl who says she's sent him a birch leaf. Unfortunately, the leaf he removes from her glassine envelope is a maple leaf. (Note: there was no indication that this was supposed to be her mistake.)
Other mistake: Across the show, several times doctors looking at an x-ray picture say things like, "Looks like he swallowed a whole junkyard" or "His belly is full of shrapnel." In fact, shrapnel, being metal fragments, should show up as clear white spots on the x-ray pictures, but none of that is visible in any of the x-rays shown throughout the show.
Factual error: While watching the Sonja Henie movie "Sun Valley Serenade" Colonel Potter says at one point of the movie "This is supposed to be where she does a triple axel and ends up in a split." Then he has to leave and says "Now I'll never get to see it." He wouldn't be able to see it until 1989 when Midori Ito from Japan was the first woman to complete a triple axel in competition, Tonya Harding was the 2nd woman to complete one and the only American woman. And I doubt Sonja Henie ever did anything as complicated as a triple axel even with her 3 Olympic Gold Medals.