From MASH, I was thinking either Radar O'Reilly or Margaret Houlihan. Or even Max Klinger, originally a one-episode throw-in who became a major member of the team.
Radar and Hot Lips (played by Sally Kellerman) were both characters in the original MASH movie, albeit Radar was a fairly minor one. So was Klinger. (Who, by the way, had to ditch the cross-dresser schtick because the homo crowd took offense and the show became more and more PC).
Klinger was at best the 2 minute fun role in the series. When they moved to more TV time I could not stand him, or for that matter MASH in general after Col. Blake and Trapper John left. So basically I like the first three seasons and you can keep the rest. I got where I could not stand Alan Alda, did not like B.J., Col. Potter or Major Winchester.