I met Charlotte Brown back in the 90s and she said that the mistake they made with Rhoda was marrying her off too early in the series. Rhoda married in episode 8 of the first season but by the end of season 2, they didn't know what else to do to keep the series from becoming trite which was then when they decided that Joe and Rhoda separate. IMO, they should have had Rhoda get pregnant but Charlotte said that they producers for some reason decided that Rhoda was funnier when she was single. Unfortunately, fans of the series didn't like a divorced Rhoda and the series was cancelled after season 4.