I watched this show when it was originally broadcast. Although it was cute, it didn't quite have the oomph to be a sustainable series. I love Abe Vigoda's look, especially his long-suffering, sad-eyed expression, but it was hard to hang a whole show around his character. Fish was better as a supporting role.
Although Bernice provided the nurturing for the kids, Fish loudly claimed to dislike them and long for a quieter life. My favorite quote from the show was when he blew out the candles on a birthday cake. The girl asked, "Did ya get ya wish, Mista Fish?" and he replied, "NO, you're ALL STILL HERE!"
Although later shows managed to center a sitcom around a negative character, such as Dabney Coleman ( http://www.imdb.com/name/nm0001056 ) in Buffalo Bill ( http://www.imdb.com/title/tt0084992 ), or the puppet alien in ALF ( http://www.imdb.com/title/tt0090390 ), these succeeded because the bad boy was SO extremely bad that you couldn't help laughing. Quietly grumbling Fish with a (well hidden) soft side just didn't go far enough to grab and hold an audience.