Wade "Unique" Adams (Alex Newell) is a recurring character in seasons 3, 4 and 6, and a main character in season 5.
She first appears in the third-season episode "Saturday Night Glee-ver" as a new featured singer in Vocal Adrenaline who is a fan of both Mercedes and Kurt despite being a competition rival.
The initial main cast encompassed club director and Spanish (later History) teacher Will Schuester (Matthew Morrison), cheerleading coach Sue Sylvester (Jane Lynch), guidance counselor Emma Pillsbury (Jayma Mays), Will's wife Terri (Jessalyn Gilsig), and eight club members played by Dianna Agron, Chris Colfer, Kevin Mc Hale, Lea Michele, Cory Monteith, Amber Riley, Mark Salling and Jenna Ushkowitz.
For the second season, formerly recurring cast members Mike O'Malley, Heather Morris and Naya Rivera were promoted to the main cast.
Mc Hale explained that the diversity of the cast's backgrounds reflects the range of different musical styles within the show itself: "It's a mix of everything: classic rock, current stuff, R&B. You won't always recognize it." Agron said in a 2009 interview pertaining to her casting session: "I nearly bailed on my audition for the show. With her wholesome good looks, Agron certainly looked the part, but the producers wondered if she appeared too innocent.
Agron said in an interview: "They told me to come back with straight hair and to dress sexier.
Although Colfer had no previous professional experience, Murphy was so impressed by Colfer's performance that the role of Kurt Hummel, named after the character Kurt from The Sound of Music, was created for him.
The series has many supporting characters, including faculty members, students and relatives of the glee club members.
Broadway stars including Idina Menzel, John Lloyd Young, Jonathan Groff, Phoebe Strole and Kristin Chenoweth have been featured in guest roles.
Auditioning actors with no theatrical experience were required to demonstrate their ability to sing and dance.
Jayma Mays (Emma Pillsbury) auditioned with the song "Touch-a, Touch-a, Touch-a, Touch Me" from The Rocky Horror Show, while Cory Monteith (Finn Hudson) initially submitted a tape of himself acting only, and was requested to submit a second, musical tape, in which he sang "a cheesy, '80s music-video-style version" of REO Speedwagon's "Can't Fight This Feeling".