"Mattress", also known as "Once Upon a Mattress", is the twelfth episode of the American television series Glee. The episode premiered on the Fox network on December 2, 2009. It was written by series creator Ryan Murphy and directed by Elodie Keene. In "Mattress", the glee club discovers that they are going to be omitted from the school yearbook. Club member Rachel Berry has the team cast in a local mattress commercial in an attempt to raise their social status. Glee club director Will Schuester discovers that his wife Terri has been faking her pregnancy.

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.