Penny Marshall worked the milk and Pepsi joke in based on her own life because as a child her mother would fill the same cup with milk as later with Pepsi and often wouldn't rinse out the cup or even wait until it was empty.
Frustrated at TV shows constantly repeating who the characters are and what they do, Penny Marshall came up with the idea of Laverne having L's on all her clothes, figuring that would solve the problem. To her chagrin, they still had to say on a regular basis who was who and where the girls worked; she got tired of all the times Cindy Williams would say 'Laverne' in an episode.
When Cindy Williams departed during the 1982-1983 season, due to pregnancy, her absence was explained by having Shirley moving out of the apartment to be with her husband Walter after he was transferred out of the country.
Michael McKean and David L. Lander were originally hired as writers/consultants. They wrote themselves into the show as Lenny and Squiggy, two characters they created in college. Squiggy was originally named "Ant'ny" but the producers wanted the two boys' names to coincide with the girls'. Squiggy was the name of an unseen character in McKean and Lander's "Lenny and Ant'ny" sketches.
Gary Marshall has said in interviews that Cindy Williams and his sister, Penny Marshall, were immature during the production of Laverne and Shirley and did not handle stardom well, treating their coworkers in an abusive manner, and acting like prima donnas, endlessly fighting about who got more lines, etc.
While still a defensive end with the L.A. Rams, actor Fred Dryer made his television debut in a 30 second spot as a lifeguard in Laverne's dream sequence in the 6th season premiere "Not Quite New York".
The cast, crew and creative forces all realized the change hadn't helped, but had rather hurt, the show when the girls moved west to Burbank in season 5. But short of resolving everything with a it-was-all-a-dream episode (which hadn't been done on television yet), they didn't know how to fix it, so they just soldiered on.
This show was #1 for two seasons and has a fervent cult following. But the critics were not kind to this show, in fact the reviews were as bad as they come; much worse than the parent show "Happy Days".
Gary Marshall has said in interviews that when he conceptualized this show he was basically re-doing Lucy and Ethel schtick from "I Love Lucy". This makes sense since Marshall himself worked for Lucille Ball on "The Lucy Show" before starting the long run of his own productions which began with "The Odd Couple".
Originally the full title of the show was officially "Laverne Defazio and Shirley Feeney", " Laverne and Shirley" for short. At least that's what the opening credits said for the first couple episodes.
Penny Marshall has said her favorite episode is "Why Did The Fireman?...", one of the few very serious episodes on the show. The plot has Laverne's boyfriend Randy ( played by Ted Danson) dying while fighting a fire. Laverne becomes depressed and goes into denial, and then her father has to talk her out of it.
Charles Grodin appeared on an episode of Laverne and Shirley as himself. In the episode both Laverne and Shirley are madly in love with him, and Lenny and Squiggy are totally starstruck. This doesn't make any sense because in the 1960s when this episode is supposed to take place, Charles Grodin was a little known TV actor and hadn't done any movies yet.