Most under-utilized characters on the show?
Similar to the question about under-rated actors on the show, which character was under-utilized. I'd nominate Colonel Flagg, but he was in the spotlight at least a few times.
I might have to nominate Nurse Ginger. She was a petite, black, female nurse in the Army in the 1950s, but very little revolved around her. Pairing her up with a large, white, uneducated Marine at an aid station seems like an easy story to write with plenty of room for issues and differences.
Even Nurse Kellye got the spotlight a few times, but in "The Nurses" episode, Margaret was the only series regular nurse featured in the episode.
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I blame autocorrect.
You may all go to hell, and I will go to Texas.