'Glee' declares 'I Am Unicorn' in the second episode of Season 3, and we'll finally find out the story behind Brittany's stuffed pony. In this episode, the cast will perform two musical tunes from 'West Side Story,' as well as one from 'Funny Girl' -- and that we'll get to meet the baby Quinn gave up for adoption in Season 1.

Broadway's Idina Menzel will make her small screen return as Shelby Corcoran, the former Vocal Adrenaline coach, who is allegedly on board at McKinley to start another glee club. She and her birth daughter, Rachel, will give a stage duet of 'Somewhere,' and she'll also be bringing back baby, which will definitely be the highlight of the episode. The kid is a a baby blend of Puck and Quinn, how much more bada--- could it get?

Meanwhile, Mr. Schue will start a  glee club boot camp, and the kids will audition for 'West Side Story,' hence the double-team of show songs. With only one coveted male lead, Blaine, Finn, Kurt and Mike will go on a quest to carry the torch, which could cause problems for Blurt/Klaine. Drama!

'I Am Unicorn' airs on FOX on September 27.

‘I Am Unicorn’ Episode Song List:
- Rachel and Shelby Corcoran (Idina Menzel), ‘Somewhere’ ('West Side Story')
- TBA, 'Something's Coming’ ('West Side Story')
- Kurt, 'I Am The Greatest Star’ (From ‘Funny Girl’)