Wikipedia
"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 ( Matthew Morrison) attempt to create a wedding medley in the style of a mash-up for his colleagues Emma ( Jayma Mays) and Ken ( Patrick Gallagher). Students Finn ( Cory Monteith) and Quinn ( Dianna Agron) find that they are no longer considered popular, while glee club members Rachel ( Lea Michele) and Puck ( Mark Salling) become romantically involved, as do cheerleading coach Sue Sylvester ( Jane Lynch) and local news anchor Rod Remington (Bill A. Jones).
The episode features covers of five songs. Studio recordings of three of the songs were released as singles, available for digital download, and three are included on the album Glee: The Music, Volume 1. Neil Diamond was hesitant about licensing his song " Sweet Caroline" to the show, but was convinced by series music producer P.J. Bloom and ultimately enjoyed the performance given by Salling. The episode was watched by 7.24 million US viewers. Musical performances received mixed reviews from critics. The Wall Street Journal Raymund Flandez described "Mash-Up" as a "turning point" for Glee, praising the episode for its character development.