Harry Morgan had trouble finding the right personality for Col. Potter when he joined M*A*S*H

Season four was a time of change for MAS*H. The real Korean War lasted three years, so perhaps it was unsurprising that the television show would have to get creative after the same amount of time. The dramedy kept things fresh by shaking up the cast. Henry Blake (McLean Stevenson) and Trapper John (Wayne Rogers) left the series. Enter Mike Farrell as B.J. and Harry Morgan as Col. Potter.

The one-hour, two-part “Welcome to Korea” introduced B.J. Hunnicutt to kick off the fourth season. “Chain of Command” welcomed Sherman T. Potter to the 4077th as its new commanding officer.

In August 1975, a syndicated UPI column introduced Morgan as the newest MAS*H cast member to the newspaper readers of America. “Morgan is low-key. He exudes warmth and dry humor,” the writer observed. “His soft sell, unobtrusive quality probably is the reason he holds the record for most series as a star performer.”

That’s right — at that point in television history, Morgan had starred as a lead in more TV shows than any other actor. That list of series on his resume included December Bride, Pete and Gladys, The Richard Boone Show, Kentucky Jones, Dragnet, The D.A., and Hec Ramsey… all packed into the span of 20 years. The actor born Harry Bratsberg was no stranger to replacing beloved characters, either. He had done just that as Sgt. Friday’s partner in the 1967 Dragnet reboot.

Pete and Gladys — in which Morgan played straight-man husband Pete Porter to scatterbrained wife Gladys Porter (Cara Williams) — came the easiest to him.

“My favorite was Pete in Pete and Gladys because I just played myself,” Morgan admitted to the UPI journalist.

“Until now Morgan has found it easy to slip into his characterizations,” the writer noted. “But he’s having trouble fitting himself inside the skin of Colonel Potter.” What was the obstacle? For starters, the still-looming shadow of McLean Stevenson hung over the Morgan.

Morgan even considered using an iconic piece of Henry Blake’s costume.

“I wanted to keep that fish hook hat he wore,” Morgan admitted, “but McLean took it with it him.”

“I’d like to make the colonel a little more wacky,” he added. “It’s taking me time to find the right niche for this guy.”

Morgan explained that he preferred comedy to drama, but he appreciated that MAS*H was not “typical fluffy situation comedy,” perhaps a slight dig at his roots on December Bride and Pete and Gladys — or, at least, an admission that he was ready to try something different.

To his credit, he nailed the persona of Colonel Potter. Without making him “wacky” or wearing a leftover fishing hat.