Quinn and Puck gather in this scene from Glee's 100th episode and pay tribute to Finn Hudson.

Dianna Agron is back on Glee. As Quinn, she pays tribute here to Finn.

Puck stops and pays tribute to his fallen teammate in this emotional scene from Glee's 100th episode.

Rachel and Mercedes are back at William McKinley. Isn't it nice to see them?

Will inspires the troops in this scene from Glee's historic 100th episode.

It's time to dance on Glee - and for good reason! The how has now aired 100 episodes.

Sing it, Mercedes. She is one of many returning characters on Glee's 100th installment.

Rachel is back in Ohio. She makes a triumphant return on Glee's 100th episode.

Sing it, Kurt! This lovable former student is back at his old stomping grounds on Glee.

Becky is all smiles in this scene from Glee, as she stands around in the show's monumental 100th episode.

Looking sharp, April! This fun character is back for Glee's 100th episode.

Sue is in deep thought. She's likely trying to think of how to best celebrate Glee turning 100.

It's like the old times on Glee! This is courtesy of the aptly-titled episode "100."

We've missed seeing these two together. Santana and Brittany are back to celebrate Glee turning 100.

Santana is back in Ohio. She makes an appearance on the show's 100th episode.

Mercedes is back! She returns home for the 100th episode of Glee.

Lemon doesn't look like she's enjoying this shin dig even the the 1920s costume looks amazing on her on the return of Hart of Dixie.

Will gathers the troops in this special Glee scene. It is from the show's 100th episode.