1975 was a critical year for M*A*S*H. The show had some personnel shakeups that could have ruined its momentum going into its fourth season. But, actors are people, and people move on to other things. Wayne Rogers, M*A*S*H‘s Trapper John, left the show due to a contract dispute with the producers. In addition, McLean Stevenson, who’d led the 4077th as Lt. Col. Henry Blake, was out as well. Stevenson was tired of not being the show’s star and cited systemic issues within 20th Century Fox for his departure.
M*A*S*H is frequently lauded as the greatest ensemble comedy in American television history. That is attributable to the chemistry of the actors on set. The interplay between the characters was critical; sure, Hawkeye was arguably the main character, but only because he had the best jokes. The stories depended on a web of lives. M*A*S*H was only as good as its ensemble, so what would they do when that group was reshuffled in ’75? One answer, of course, came in an episode from the previous year, “The General Flipped at Dawn.” That season three show saw Harry Morgan tagging in for just one episode, in which he confirmed the producers’ inkling that he’d make a great addition to the cast
So, in season four of M*A*S*H, a new character played by Morgan, Colonel Sherman T. Potter, is seamlessly integrated into the 4077th. Morgan had the benefit of being a bonafide TV commodity; he’d already been a regular on six other shows dating back to the ’50s. The writers knew what he was capable of and built the character of Col. Potter around Morgan’s strengths. They even took input from Morgan’s real life to give the Colonel a realistic feel.
Col. Potter was a cavalryman, partly due to Harry Morgan’s love of horses. According to an article in the Chicago Tribune, M*A*S*H‘s writers implored Morgan for such details. Those particulars were crucial to shaping a character that felt real. Where Henry Blake’s fishing gear once hung, now there is Col. Potter’s “Black Jack” Pershing cavalry hat. Morgan’s fondness for animals also influenced the dialogue, with Col. Potter often reminiscing about old horses.
Morgan’s affability was definitely to thank for the casual rapport between Col. Potter and Gary Burghoff’s Radar O’Reilly. Radar was pretty tight with Lt. Col. Blake and frequently finished the commanding officer’s sentences and predicted his needs. It should follow, then, that Radar would be hesitant around this new character in Col. Potter. However, Harry Morgan quickly hit it off on set with Burghoff, and that trust also came through onscreen.
The role was more fun for Morgan to play too. On a previous show, Dragnet, Morgan had been instructed to act with an unwavering monotone, befitting an authoritative law enforcement officer. But with M*A*S*H, Morgan was able to really play, and have fun and laugh as Col. Potter, allowing for a much more enjoyable experience.