For the show's first season, the theme song was performed by the popular family group The Cowsills. For the rest of the show's run, it was performed by The Charles Fox Singers, who were a group of Los Angeles studio musicians that did numerous radio and television commercials.
Every story in the series, and many of the "blackout" vignettes in-between, featured a large, brass bed. This is probably an homage to The Bed (1968) by James Broughton, an experimental poet and filmmaker whose works were an influence on the Beat poets of the 1950s. "The Bed" is an award-inning 20-minute short that was filmed during the 1967 "Summer of Love" in San Francisco, CA. It featured several nude men and women cavorting on a large, brass bed in a garden.
Many of the blackouts were credited to Samuro Mitsubi and Tawisaki Kwi. According to the book "My Happy Days in Hollywood" (2012), the names were pseudonyms for memoir author Garry Marshall and his long-time writing collaborator Jerry Belson.
"Happy Days" (1974) was not a direct spin-off of this show, but an indirect one. Garry Marshall (I) pitched a show to ABC called "New Family in Town". The network turned it down. So Marshall did a vignette on an episode of this show with the three characters. Two years later, American Graffiti (1973) became an unexpected success. The network remembered Marshall's show. It asked him to shoot a pilot with some changes. It wanted a gangster-type character to intimidate Cunningham. Thus, the birth of Fonzie.