Happy Days S02 E20 Fish and the Fins

"Those were the days of the 1950's...filled with innocence and the promise of even better days to come."

To hide from overzealous fans, a popular rock group (one of the members was Richie's childhood friend) is staying at the Cunningham house, but Richie can't tell anyone that they're there. This poses a problem for Richie because nobody believes he actually knows them.