According to Fox's "Behind the Scenes in Brittany's Bedroom," Brittany has 30 notches carved into her bed to represent her "conquests." They can be seen on the front left top rail.
In a "blink and you'll miss it" moment, while the kids are voting for the winner of the duets competition, you'll notice that Mercedes (who performed with Santana) votes for "Mercedes & Satan" in an obvious jab at Santana's attitude and reputation
Rachel (Lea Michele) and Kurt (Chris Colfer) sing a medley of the songs "Happy Days Are Here Again" and "Come on, Get Happy." This combination and arrangement was first performed by Barbra Streisand and Judy Garland on an October 1963 episode of "The Judy Garland Show." Rachel's and Kurt's costumes in this scene are also nods to the Garland-Streisand duet: Streisand wore a white satin sailor-style blouse with a dark tie and Rachel wore a replica of that top; Garland wore a shiny dress and Kurt wore a shiny suit.
This episode is featured in The Office episode titled "Viewing Party." Steve Carell's character "Michael" states that his favorite Glee character is "the invalid," meaning Artie played by Kevin McHale. Kevin previously appeared in an earlier episode of The Office titled "Launch Party."