In the show's later seasons, M*A*S*H tended to have a more serious tone to its episodes. Such is the case when he loses his eyesight. We see him in a vulnerable state, something that rarely happens to the character.
The Death of Henry Blake
McLean Stevenson came to tire of playing Henry Blake. That was part of the reasoning to kill off Henry on M*A*S*H. His sendoff included a tender moment between him and Radar, played by Gary Burghoff.
The Arrival of Sherman Potter
With Stevenson's character leaving M*A*S*H, a new commanding officer was needed. Enter Colonel Sherman Potter, played by Harry Morgan. Eagle-eyed Potter enters the 4077th only to look over and see Radar trying to get some sun.
Margaret Becomes Pregnant
In the show's early seasons, people saw Margaret, played by Swit, be involved with Major Frank Burns, played by Larry Linville. But she would end up getting married to someone else and while with her husband, she became pregnant.