happy days is my benny and joon.
Look what I found on Wikipedia:
http://en.wikipedia.org/wiki/Love%2C_American_Style#Happy_DaysHappy DaysGarry Marshall likes to say that "Love, American Style" was where failed sitcom pilots went to die. And there was much truth to that. Many times, if a TV producer couldn't find a network interested in a sitcom pilot he'd made, he'd sell the unused videotape to Aaron Spelling, who'd use the funniest bits of the pilot as a segment on "Love, American Style."
In 1972, Garry Marshall came up with a concept for a sitcom about teenagers growing up in the Fifties, and shot a Happy Days pilot starring Ron Howard (as Richie), Marion Ross (as Richie's mother), Anson Williams (as Potsie, Richie's friend), among others. Roles played in the episode by Harold Gould (Howard the father), Susan Neher (Joanie, Richie's sister), and Ric Carrott (Chuck, Richie's brother) were played by other actors in the spin-off. Marshall tried, unsuccessfully, to sell the sitcom to all three networks, but was unsuccessful. At last, he sold the pilot to Aaron Spelling, who aired the show in February 1972, as "Love and the Happy Days."
Shortly afterward, the movie American Graffiti and the Broadway musical Grease, led to a wave of nostalgia for the Fifties, and ABC executives decided to buy Marshall's new series, which became a huge hit.