FOX's Glee presents "Mash-Up," which actually features not a single mash-up song. But it does have several clashes, or mash-ups, between characters. Will (Matthew Morrison) helps Ken (Patrick Gallagher) and Emma (Jayma Mays) prepare for their wedding dance. Ken gets angry about being a consolation prize to his bride, so he forces the football players to choose between the team and glee club to get back at Will. Sue (Jane Lynch) also takes advantage of Will's dancing techniques, only to be disappointed in turn by her own beau, Rod Remington (Bill A. Jones), the reporter. Quinn (Dianna Agron) and Finn (Cory Monteith) seek to regain their popularity, while Puck (Mark Salling) takes a romantic interest in Rachel (Lea Michele).
Perhaps the more appropriate title for this episode of Glee would be "Will Can Dance." Matthew Morrison certainly gets no shortage of time to show off his impressive dancing talents, as if a certain amount of doing so is required in his contract, and the writers decided to cram it all into one episode. He boogies through "Bust a Move" and "Thong Song." He sweeps Sue off her feet with "Sing Sing Sing (With a Swing)," and also does somewhat the same for Emma in "I Could Have Danced All Night." That's a full two thirds of the music featured in "Mash-Up," and in half of those, Will doesn't even sing. Morrison has the talent to pull off such a decision, but it also makes the teacher look a little like a show off. Thankfully only one number is in front of the New Directions.
It's interesting that not a single one of the songs mentioned above, nor "Sweet Caroline" and "What a Girl Wants," two solos covered in this episode, are part of a mash-up. Glee uses the trick of combining two songs into one many times in the series, but ironically, in "Mash-Up," has not one actual instance, using the episode title metaphorically. It can be applied to Ken and Emma's personalities. The episode also features budding, and quickly ending, new relationships. Then, there is the case of conflicting school activities. Will does ask the kids to come up with a mash-up, and tries to write one himself. But none of those efforts ever make it on screen.