off the skills of Heather Morris". Prior to appearing in Glee, Morris was a back-up dancer for Beyoncé. She was originally hired as a choreographer to teach cast members Colfer and Jenna Ushkowitz the "Single Ladies" dance. A week later, she was cast as cheerleader Brittany. Morris had a recurring role throughout the first season, and was promoted to a series regular for season two. At the 2010 Television Critics Association Summer Press Tour, Murphy stated that Brittany would have "big storylines" in the new season, as viewers want to know more about her. Stamos makes his first Glee appearance in "Britney/Brittany" playing Carl Howell, a dentist and Emma's love-interest. Other recurring characters who appear in the episode are glee club member Mike Chang (Harry Shum, Jr.), Principal Figgins (Iqbal Theba), Coach Shannon Beiste (Jones), school reporter Jacob Ben Israel (Sussman), cheerleader Becky Jackson (Lauren Potter), school bullies Dave Karofsky (Max Adler) and Azimio (James Earl) and student Lauren Zizes (Fink). So You Think You Can Dance contestant Mark Kanemura appears as a backing dancer. Music The episode featured cover versions of five Spears songs, two of which were performed by Morris. "Stronger", "...Baby One More Time", "Toxic", "I'm a Slave 4 U", and "Me Against the Music" (featuring Madonna) were covered. "The Only Exception" by Paramore and "Sailing" by Christopher Cross were also performed. All songs except "Sailing" were released as singles, available for download, and all songs except "I'm a Slave 4 U", "...Baby One More Time", and "Sailing" are included on the album Glee: The Music, Volume 4. Both Spears and Paramore's Hayley Williams praised the episode via the social networking website Twitter, approving of the use of their songs. All singles managed to chart on the Billboard Hot 100, selling 406,000 downloads collectively. The cast's cover of "Toxic" charted as the highest of the six, at number sixteen with 109,000 downloads. Tim Stack of Entertainment Weekly felt that the performances of "I'm a Slave 4 U" and "Me Against the Music" fell flat, opining that Glee best musical numbers are the ones which twist, rather than imitate the original versions. Though he praised Morris' dancing, he felt the episode revealed her to be "not a standout vocalist". Conversely, Erica Futterman of Rolling Stone enjoyed the direct recreations of iconic Spears moments in "I'm a Slave 4 U", and MTV's Aly Semigran called it one of the