"Mash-Up" is the eighth episode of the American television series Glee. The episode premiered on the Fox network on October 21, 2009. It was written by series co-creator Ian Brennan and directed by Elodie Keene. The episode sees glee club director Will Schuester attempt to create a wedding medley in the style of a mash-up for his colleagues Emma and Ken. Students Finn and Quinn find that they are no longer considered popular, while glee club members Rachel and Puck become romantically involved, as do cheerleading coach Sue Sylvester and local news anchor Rod Remington.

William Michael Schuester, often referred to as Mr. Schue, is a fictional teacher character and one of the two main protagonists from the Fox musical comedy-drama series Glee, alongside his student Rachel Berry. He appeared in Glee from its pilot episode, first broadcast on May 19, 2009. Will was portrayed by Matthew Morrison, and was developed by Glee creators Ryan Murphy, Brad Falchuk, and Ian Brennan. He is a Spanish teacher at the fictional William McKinley High School and the director of the show's titular glee club in Lima Ohio, where the show is set. He ultimately becomes the school's principal. His storylines have seen him revive the school's failing glee club, leave his wife Terri, win the love of school guidance counselor Emma Pillsbury, and marry her.