This may be the guest role that Neil Patrick Harris was born to play. The actor has already shown off his musical chops on Broadway, starring in 'Cabaret' and 'Sweeney Todd,' to name just a couple of shows. Now, he gets to appear on 'Glee' (Tue., 9PM ET on Fox).

[Spoiler alert.]

Harris plays the old rival of Will Schuester (Matthew Morrison). Harris's character felt that he was bound to be a famous performer, but soon spiraled downward into drug addiction. He returns to town to take revenge on Will, and the two of them soon find themselves competing over the same role in a local production of 'Les Misérables.' To make matters worse, both of them insist on singing the same song at their audition.

The director of the play forces them to perform a duet. Will the pair learn something by singing together? Can they manage to bury the hatchet via the power of music?