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Fall Out Boy did their best Spinal Tap impression on Wednesday night's episode of "Late night with Conan O'Brien."  The group's performance of their new single "My Songs Know What You Did in the Dark" featured a number of references to the classic 1984 mockumentary "This Is Spinal Tap" - including mini Stonehenge and one of the film's stars, Harry Shearer, on bass. 

He stepped in for Fall Out Boy bassist Pete Wentz after he got stuck in a giant egg-like stage prop, just like Shearer did in the original movie!. 

"My Songs Know What You Did in the Dark" is featured on Fall Out Boy's comeback album Save Rock and Roll, which arrived in stores earlier this week. You can get Fall Out Boy's new album here.