The show underwent several changes over the years. There was originally an older Cunningham brother, Chuck, who went away to college and disappeared from the show. Fonzie, perhaps best described as a hood with a heart of gold, was originally a minor character, but the show focused increasingly on him over time, culminating in an episode that spawned the term "Jumping the shark".
Happy Days was entertaining for not being totally comedic. It often developed storylines from timeless human conditions such as friendship, courage, sacrifice, love, loyalty, etc. Its characters not only dreamed of growth but succeeded despite their limitations. They also knew failure and loss. Many viewers found the characters easy to relate to.
The show originated during a period of 1950s nostalgia in film, television, and music. It began as an unsold pilot called "Love and the Happy Days" on the TV series Love, American Style. Then, in 1973, George Lucas released a film with a similar theme, American Graffiti (co-starring, in a twist of irony, Ron Howard and Cindy Williams). The success of the film caused series creator Garry Marshall and ABC to reconsider the unsold pilot and make Happy Days as a series. One spinoff show, Laverne and Shirley, co-starring Cindy Williams and Penny Marshall, also took place in the same '50s time period.
Happy Days also spun off four different live-action series (Blansky's Beauties, Mork and Mindy, Out of the Blue, Joanie Loves Chachi), and two animated series (Fonz and the Happy Days Gang and Laverne and Shirley in the Army).
Ron Howard, who had starred as a child actor in The Andy Griffith Show, went on to direct several critically acclaimed films, including Apollo 13 and A Beautiful Mind. Tom Bosley (Richie's father) continued acting and appeared in other sitcoms.