 The original title of the series was to be simply "Kotter," but that  was before composer Sebastian, John (I) (qv) had difficulty  writing the theme song lyrics. He couldnt find enough rhyming words  for the title. Giving up on that tack, he decided to compose lyrics  that illustrated the premise of the show in a song called, "Welcome  Back." The producers were so impressed with the song that they  decided to change the series title to "Welcome Back, Kotter." The  song was also released on a single which went to #1 on the charts.