The Days were once Happier

Joe and Cate ask each other about television in their early letters to each other. One of the popular shows in 1979 that they could've watched was Happy Days. During this time, the show had fallen to 17th in the ratings. Three years earlier, Happy Days was the most popular show, it spawned spin-off shows, comics, and cartoons. In 1979, things were different. 

The show started in 1974 starring Ron Howard. The early success could be attributed to a recent movie called American Graffitti, which also starred Howard. The first season showed Howard's character, Richie and his friends get in trouble, meet girls and hang out. 

The early friends were Potsie, played by Anson Williams, Ralph played by Donny Most and Henry Winkler's character The Fonz. 

As the show progressed, Ron Howards character shared the spotlight with Henry Winkler's. I've never read that this created any tension or competition for the spotlight. If anything, it gave Ron Howard a chance to star and direct a movie called Grand Theft Auto.

1979 was Howard's last year on the show. Don Most will also leave that year. While Ron Howard is a popular director, Don Most continues to work every year according to IMDB. 

The vacuum of Howard and Most leaving didn't create a spotlight for Anson Williams. I haven't read his book, so I don't know his opinion on that. His character went from a merry prankster in season 1 to being a minor character of little intelligence. 

New characters were brought up to fill the hole by Ron Howard's departure.

Happy Days will continue to run for another four years, but to decreasing ratings. 

Most of this information came from Wikipedia and what I remember at the time.