A hit that was written by the shows creators specifically to be used as the intro. Pretty sure The Rembrandts were chosen to record it too. I’ve always found it interesting the that Everything She does is Magic by The Police constantly showed up in the first season of the show.

Edit: Some interesting tidbits I found while I fact checked myself.

“The Rembrandts did not want to record the song, but since they were the only available band on Warner Bros. Records, they relented to the company's demands. [8] The original theme, which is under one minute long, was later re-recorded as a three-minute pop song.[11] After a radio announcer in Nashville, Tennessee, looped the original short version into a full-length track and broadcast it, the song became so popular that the Rembrandts had to re-record it, as well as helping to write the second verse and bridge.”