In Season 2's "For Want Of A Boot", Frank's birthday is on a cold winter day. In this show, his birthday has changed to a warm day in spring.
When Colonel Potter is holding the brochure about the writing course, Radar tells him to look at page 3. Potter opens the brochure and reads what Radar is referring to. Judging by the number of pages that can be seen to the left of where he is reading, he has to be at least on the page 4-5 spread, if not the page 6-7 spread.
While Hawkeye is telling his amusing anecdote about the squirrel to Radar, he says that when he looked up the answer for the number of bones in the human hand, the answer was 28. There are actually 27 bones in the human hand.
Father Mulcahy says that his sister can "slam dunk" wearing a heavy crucifix. That term, according to Webster's, wasn't used until 1972.
When sitting down at the table, Major Burns refers to Jeff Maxwell's character (Igor), as "Sergeant", but Igor is wearing Private's stripes.
In his letter home, Radar mentions his nephews. It was established early on that he is an only child. He couldn't have nephews.