Get your disco ball, platform shoes, and polyester suit! The Glee cast goes back to the 70s for a tribute to "Saturday Night Fever."

Jenna and Kevin break down all the groovy details of this episode, including revealing that Cory was upset during dance rehearsals, what it was like for Jenna going back to dancing after her back injury, and did you catch it? Kevin points out the scene where he was totally checked out!

Plus, the return of Jesse St. James, the debut of Alex Newell's 'Unique,' and Jenna reveals feeling weird shooting one scene in particular and what it was like being on the actual dance floor from "Saturday Night Fever!"