It's hard for me to say exactly why he is so funny. Maybe it's in the way he tried to "be bad" but, deep down, he was a good hearted person and it showed through in the end. His schemes were just plain goofy and he got his own way most of the time. Rosco is one of a kind for sure. In my opinion, Rosco was critical to making that show work. The way he and boss Hogg played off one another was priceless and probably couldn't be duplicated by anyone but Rosco P. Coltrane.