"Glee" premiered on Fox in May 2009 and introduced fans to rising stars like Lea Michele, Cory Monteith, and Chris Colfer.
Throughout the show's six-season duration, lots of notable stars appeared. Singers like Britney Spears, Demi Lovato, and Josh Groban had guest-starring roles on "Glee." Other actors, like John Stamos and Gwyneth Paltrow, also popped up on the series.
Here are 41 people you probably forgot appeared on "Glee."
SEE ALSO: 57 celebrities you forgot guest-starred on 'How I Met Your Mother'
FOLLOW US: INSIDER Entertainment is on Facebook
He appeared on season three after hearing about Rachel and Finn's engagement.
Rachel's dads pretended to be supportive of her engagement.
She worked a the Spotlight Diner in New York City with Rachel, Santana, and Kurt. Lovato performed an acoustic rendition of The Beatles' "Here Comes the Sun" with Naya Rivera's Santana during her first appearance on "Glee."