Hawkeye jokingly tells Radar during the movie that Shirley Temple is 42 years old. On the air date, she was 47 years old. During the time depicted, she was in her early 20's (23 in 1951.)
The Shirley Temple movie being watched is The Littlest Rebel (1935), featuring Temple as the daughter of a rebel officer living on a Southern Plantation. Thus, when Hawkeye responded to Col. Blake that he missed the Civil War starting, it was actually appropriate.
Margaret says she has a younger sister who is getting married. Margaret says that her sister's also in the military but is 'only a Captain'.