Sneak Peek - Mercedes Feels The Retro 'Glee'

By ET ONLINE

While Rachel Berry strives for stardom, Mercedes and Santana are busy delivering star-making musical moments every single week on Glee.

The two-some stage an unofficial Troubletones reunion in Tuesday's episode when they burn up McKinley with a fiery rendition of Disco Inferno!

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The throwback performance is just one of many in this week's disco-themed episode, which sees New Direction looking to the past in order to make their future groovier.

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Check out a sneak peek from Tuesday's all-new episode and tune in to Fox at 8 p.m. for more far-out performances.