Taylor Swift and Zac Efron appeared on 'The Ellen Degeneres Show' today, where they not only promoted their new animated film, 'Dr. Seuss' The Lorax,' but also performed a duet set to the sounds of Foster the People's 'Pumped Up Kicks.'

　　The 22-year-old country singer explained that she had given her co-star a guitar lesson, and complimented him by saying he was "really good at it." Then Tay and Zac broke out into a rendition of Foster the People's mega hit, only with new lyrics, which poked fun at Ellen.

　　But while Taylor and Zac do have chemistry, it ends on the friend level. "We are not a couple," the singer confirmed. "He's awesome -- we are not a couple, though. You hear people get together when they're shooting movies, co-stars. But not like animated co-stars. You know what I'm saying."

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