The final two-hour episode, which is entitled "2009/Dreams Come True," is described as such: "'Glee' goes back in time to find out why the original members of New Directions initially signed up for glee club. Then, 'Glee' flashes forward to see how the character’s lives have progressed five years down the road."
In addition to Tony nominee Groff, the guest cast will also include Geraldo Rivera as himself; Andrew Rannells as himself; Mark Salling as Puck Puckerman; Kevin McHale as Artie Abrams; Amber Riley as Mercedes Jones; Jenna Ushkowitz as Tina Cohen-Chang; Jayma Mays as Emma Pillsbury; Dianna Agron as Quinn Fabray; Naya Rivera as Santana Lopez; Heather Morris as Brittany S. Pierce; Jessalyn Gilsig as Terri Schuester; Melissa Benoist as Marley Rose; Jacob Artist as Jake Puckerman; Alex Newell as Unique; and Blake Jenner as Ryder.
The series cast includes Lea Michele as Rachel Berry; Chris Colfer as Kurt Hummel; Darren Criss as Blaine Anderson; Chord Overstreet as Sam Evans; Jane Lynch as Sue; Matthew Morrison as Will; Dot-Marie Jones as Coach Beiste; Lauren Potter as Becky; Becca Tobin as Kitty Wilde; Laura Dreyfuss as Madison McCarthy; Billy Lewis Jr. as Mason McCarthy; Samantha Ware as Jane Hayward; Marshall Williams as Spencer Porter; Noah Guthrie as Roderick; and Iqbal Theba as Principal Figgins.
