“4. HAPPY DAYS ACTUALLY PREDATES AMERICAN GRAFFITI.
George Lucas’s Oscar-nominated 1973 film American Graffiti launched a craze for 1950s nostalgia (even though the movie was set in 1962). Casting director Fred Roos had worked with Ron Howard on The Andy Griffith Show and recommended him to Lucas for the role of Steve Bolander. Lucas dug out the “Love and the Happy Days” episode of Love, American Style to determine whether Howard could play an 18-year-old high school student convincingly. Once American Graffiti became a runaway success, ABC decided that the time was ripe for a 1950s-era sitcom and Garry Marshall’s project was resurrected.”
http://mentalfloss.com/article/66330/14-nostalgic-facts-about-happy-days
BTW, if you play trivia and answer that “American Graffiti” came first, you lose. The “Love and the Happy Days” episode of “Love, American Style” is considered the pilot of “Happy Days.”
“Love and the Happy Days” was what it was called during syndication after “Happy Days” premiered. The original title of the segment on “Love, American Style” was “Love and the Television Set”.