In the episode where Laverne is singing at Cowboy Bill's and has a young boy as a fan (not quite "Sing! Sing! Sing!"/Hoot Night), one of the girls turns on the radio in the bedroom, and an instrumental version of Simon and Garfunkel's hit "The Sounds Of Silence" is heard.

Here's the error I found: The 1980-81 season is set in the 1964-65 timeframe. "The Sounds Of Silence" first hit the Billboard radio charts November 20, 1965 (reaching #1 the following year). Is it possible that the 1980-81 season covered all aspects of 1965 and not just the first half, as is my impression?