5. Max Klinger (M*A*S*H)
When veteran young Theatre actor Jamie Farr was cast in a walk-on role during the first season of M*A*S*H, he was never intended to be anything more than a one-off. Just a kooky soldier in drag trying to get out of the army. But Farr did it so well that the showrunners loved him, and decided to bring him back a few more times. Even then however, he still wasn't supposed to stick around. But after a few appearances the network started getting fanmail for Farr, and the showrunners realized they had an audience magnet on their hands. Klinger started appearing in more and more episodes, always in something outlandish and gaudy, always trying to fake insanity, and yet always doing his job to the best of his ability. It didn't take long for his name to start appearing in the opening credits, and he became one of only four characters to last the show's entire run, along with Hawkeye, Hotlips, and Father Mulcahey. The character was among the few who carried on to After M*A*S*H, the short-lived follow-up series set in the States after the Korean War and focusing on Sherman T Potter. It did respectable but not earth-shattering ratings in it's first season, consistently ranking around 15 in the Nielsen Ratings, but executive meddling lead to a huge ratings decline in Season 2, and lead to it being quickly cancelled when fans revolted en masse.