As we recently teased out, the 300th song is a mash-up of epic diva proportions. Two of Adele's smash hits, 'Rumor Has It' and 'Someone Like You,' are performed to perfection by the new, all-girls rival glee club, the Troubletones. Finally, Mercedes and Santana get their time to shine! Speaking of the Troubletones, teacher/director Shelby Corcoran may be getting into some big trouble herself. We'll get to see the aftermath of her totally taboo kiss with Puck, who also happens to be the biological father of her adopted daughter. Appropriately, Puck performs Van Halen's 'Hot for Teacher'!
In the meantime, congressional hopeful Sue Sylvester launches a smear campaign against her new challenger, Kurt's dad Burt Hummel -- surprise, surprise.
In addition to the momentous and divalicious 300th song, three other mash-ups are featured in the jam-packed episode. The New Directions take on Hall & Oates' 'I Can't Go for That' spliced with their 'You Make My Dreams.' 'Glee' favorite Lady Gaga is covered, yet again, with a mash-up of her 'You and I' with Eddie Rabbitt and Crystal Gayle's song of the same name, performed by Mr. Schue and Ms. Corcoran -- teacher sing-off!
As the rivalry heats up between the McKinley High glee clubs, the New Directions and the Troubletones go head-to-head with a mash-up of Pat Benatar's 'Hit Me with Your Best Shot' and Blondie's 'One Way or Another.'
Listen to all the songs from tonight's episode before it airs, below!
Listen to 'You and I/You and I'
Listen to 'Hit Me With Your Best Shot/One Way or Another'

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