Why wasn't Duke in the TV series?
Duke Forrest was a primary character in the movie and in the books, but he was never seen or mentioned on the TV show. In fact, he's the only major character who didn't get carry over, with the exception of Painless Pole, although he is mentioned in the pilot.
You have to wonder why the producers decided not to use this character. Maybe they were so busy shoving Alan Alda in our faces that they wanted to focus on as few secondary character as possible?