This episode was different from any comedies at the time and would influence others. Mclean Stevenson left the show (which he would later regret) after three seasons and the show killed his character off. When Radar walked in the operating room and told everyone what happened to Henry it was a memorable tv moment.
Sitcoms just didn’t kill characters off and Mash would start mixing comedy and drama more after this.
If it’s about my discharge, give it to me straight! I can take it!
You behave yourself, or I’m gonna come back here and kick your butt!
M*A*S*H: Abyssinia, Henry
The Characters: Capt. Benjamin Franklin ‘Hawkeye’ Pierce, Capt. ‘Trapper John’ McIntyre, Lt. Col. Henry Blake, Maj. Margaret ‘Hot Lips’ Houlihan, Maj. Frank Burns, Cpl. Walter ‘Radar’ O’Reilly, Cpl. Maxwell Q. Klinger and Father Francis Mulcahy
Radar has an announcement for Henry in O.R. Henry Blake has received his discharge: he is finally going home to Bloomington, Illinois, to his wife, Lorraine, and their children, the country club and his medical practice. The entire 4077 gang is thrilled for Henry and they wish him well; gifts are gotten, parties are thrown and all sorts of final memories are made. But, the entire gang is sad to be losing such an integral part of the 4077 gang. Radar, in particular, is losing the man who was a father to him. The final farewell formation is memorable; even Hawkeye and Trapper show up to tell their friend and leader a fond farewell. Some farewells are fonder than others. Klinger dresses to kill. As Henry starts to leave, Radar steadfastly holds his salute to his departing C.O. until Henry finally acknowledges him.
https://www.imdb.com/title/tt0763200/