"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. Santana (Naya Rivera) mercilessly taunts rival glee club member Finn (Cory Monteith), who ultimately responds by publicly accusing her of cowardice in her relationship with Brittany, thereby revealing to their fellow students that she is a lesbian. Sue Sylvester (Jane Lynch) starts a propaganda campaign against Burt Hummel (Mike O'Malley), her chief rival in the special election for congress. Principal photography for "Mash Off" occurred in October 2011. The episode features four mash-ups, including the show's 300th musical number, Adele's "Someone Like You" and "Rumour Has It", which sold 160,000 copies in its first week and debuted at number eleven on the Billboard Hot 100. All songs from the episode were released as singles available for digital download. "Mash Off" was met with a mostly positive reception from critics, and its musical performances and cover versions were also well received by reviewers. Upon its initial airing, this episode was viewed by 7.08 million American viewers and earned a 3.0/8 Nielsen rating/share in the 18–49 demographic. The total viewership was up from the previous episode, "The First Time". Plot Puck (Mark Salling) fantasizes about his substitute teacher, Shelby Corcoran (Idina Menzel), whom he recently kissed and has since fallen in love with. He sings "Hot for Teacher" by Van Halen, with Mike (Harry Shum, Jr.), Blaine (Darren Criss) and Finn (Cory Monteith). Puck tries to convince Shelby, who adopted the child he fathered with Quinn (Dianna Agron), to start a relationship with him, but she rejects the idea. Quinn still wants to get Beth, her birth daughter, back from Shelby, and tries to join Shelby's glee club, the Troubletones, to get closer to Shelby. After Puck tells Shelby of Quinn's true intentions, Shelby informs Quinn that she does not want her in Beth's life. Will (Matthew Morrison) and Shelby agree to hold a mash-up competition between the New Directions and the Troubletones. Santana (Naya Rivera) takes the rivalry very seriously, and taunts and