In the earliest days of "Glee," selling songwriters on the show, a musical comedy that tells its stories in part through cast performances of remade pop tunes, wasn't as easy as it has become.

… we’ll meet Sunshine Corazon. … will hear a cover of “Empire State of Mind.” … will be treated to new Sue Sylvester one-liners. We’ll also enjoy a slew of new additions to the Glee music catalog. In ...