all about family
I agree with the reviewer who said that the 1st 2 seasons are not for children under 10 and are, in fact, more for teenagers. The other seasons are for the whole family. At the beginning of the series Fonzie was a thug, but he soon shed that image and became more family-oriented, thereby showing viewers that people can and do change. (On occasion, though, he had the opportunity to put his street smarts to good use, beating up bad guys.) After all, the scripts had him as having a very unstable life as a child. Family was something Fonzie didn't have but clearly wanted and needed. That's why the Cunninghams took him in as a family friend, often taking him with them on major trips.