For the shows first season the theme song was performed by the popular family group The Cowsills. For the rest of the shows run it was performed by The Charles Fox Singers who were a group of L.A. studio musicians that did many 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-winning 20 minute short that was filmed during the 1967 Summer of Love in San Francisco. It featured several nude men and women cavorting on a large, brass bed in a garden.
Many of the "Love, American Style" 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.
Love American Style spun off Happy Days, which itself spun off Fonz and the Happy Days Gang. If you look at the parent show, Love American Style, a modern rom com anthology program about dating and relationships in the 60s and early 70s, and the spinoff, Fonz and the Happy Days Gang, a sci fi cartoon which featured all manners of flying saucers, monsters and aliens in every episode, the difference between the two is staggering.
Happy Days was not a spin off of Love American Style. Marshall pitched a show to ABC called New family in Town. The network turned it down. So Marshall did a vignette on an episode of Love with the 3 characters. 2 years later American Grafiti became an unexpected success. the network remembered Marshalls show. They asked him to shoot a pilot with some changes. They wanted a gangster type to intimidate Cunningham. Thus the birth of Fonzie.
The trivia item below may give away important plot points.
The Cowsills ("Hair") originally recorded the theme song,which was used in the first season. Another version by the Ron Hicklin Singers (credited as the Charles Fox Singers) was used from the second season on.