"Mash Off" is the sixth episode of the third season of the American musical television series Glee, and the fiftieth overall. The episode was written by Michael Hitchcock and directed by Eric Stoltz, and originally aired on Fox in the United States on November 15, 2011. Special guest star Idina Menzel is featured as rival glee club director Shelby Corcoran, and she and Will Schuester (Matthew Morrison) hold a mash-up competition between the Troubletones and the New Directions.