Looking over this message board back as far as it shows surprised me in that I didn't see any posts about the impossibly-confused timeline of M*A*S*H episodes. You know: like Potter arrives at the unit in Sept. 1952, but also was there for the New Year celebration of 1950/51; an episode with B.J. (arrived concurrently with Potter, thus 1952) has a radio news broadcast about Pres. Truman meeting Gen. MacArthur at Wake Island (happened in October 1950); on and on and on....... the historically astute viewer catches one or more in each episode.
After a lot of thought, I have figured it out. This is metaphysical and unsatisfying, but it is literally the only way I can find to make sense of the M*A*S*H timeline: Once the second cast is in place (Potter, B.J., Winchester, Klinger as clerk), then the FIRST CAST EPISODES NEVER HAPPENED. Henry Blake, Trapper, and Burns never existed. Potter was always the C.O., even back to 1950, B.J. was there even back to 1950; multiple seasons (climate, not TV) can happen after Potter's arrival (instead of the 3-1/2 between Sept. 1952 and the end of the war in July 1953) -- how many Winters and Summers were portrayed in the Potter years ??
I'm reminded of Jack Nicholson's exchange with "Delbert Grady" in "The Shining," and may I paraphrase:
(Potter walking out of his office at 4077 past Klinger in the outer office; stops suddenly having a Deja Vu attack) "Say, didn't a hombray named Blake used to ride tall in the C.O. saddle here?"
(Klinger) "Why no, your Colonelship!! YOU are Sultan in this tent! YOU have ALWAYS BEEN Sultan in this tent!"
Nothing else works.