Arnold
Was he ever married on the show? I guess it could be Fonzie's family too, since he was part owner.
I know nobody likes remakes (well, a lot of people anyway.) But I was thinking it would be fun to see his great-great-grandchildren (depending what era the show is set in) running a "retro" style eating place. Maybe a few main characters (who would logically still be alive, again, depending on when the show is set) dropping in once in a while.