When Glee aired its first episode in May 2009, the TV show only attracted a fraction of the viewers who tuned in for American Idol, which was shown on the same channel just one hour prior. The numbers looked bleak, but Billboard's music charts told a different story the following week, when the Glee version of Journey's "Don't Stop Believing" became a Top Five hit. Performed during the pilot by the castmates themselves, the song eventually sold...