The McKinley High production of Grease opens starring Ryder as Danny Zuko and Marley as Sandy Olsson. Santana returns to Lima to help out with the show. So do Kurt and Rachel, but things get awkward when they run into Finn and Blaine. Kitty hosts a sleepover for the girls, using it as an opportunity to undercut and bully Marley.
Singles:
Greased Lightning - Ryder and Sam with New Directions Boys
Look At Me I'm Sandra Dee - Kitty with New Directions Girls
Beauty School Drop Out - Blaine
Look At Me, I'm Sandra Dee (Reprise) - Marley
There Are Worse Things I Could Do - Santana, Cassandra, and Unique
You're the One That I Want - Ryder, Marley, Rachel, Finn, Kurt, Blaine, Brittany, Santana with New Directions
Information from Glee Wiki