From season 3 of Laverne & Shirley:
In the final scene of the episode, "Bus Stop", first shown in February 1978, the cast joins together for a rendition of "Milwaukee Moon", with Lenny (Michael McKean) on guitar. Scope it out!
In addition to Lenny & the Squigtones, series stars Penny Marshall & Cindy Williams actually released an album of their own. "Laverne & Shirley Sing" (Italics mine) was released on Atlantic Records, while the Squigtones recorded for Casablanca. Go figure.