Watch Taylor Swift and Fifth Harmony Perform 'Worth It' at Levi's Stadium

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Taylor Swift, Dina Jane Hansen, Normani Kordei, Camila Corbello, Ally Brooke and Lauren Jauregi of Fifth Harmony perform at Levi's Stadium on August 14, 2015 in Santa Clara, California.

Taylor Swift has officially become the honorary sixth member of Fifth Harmony.

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In yet another amazing cover song performance on her 1989 tour, the megastar invited the pop quintet on stage to perform their hit "Worth It" at her Friday night (Aug. 14) concert at Levi's Stadium in Santa Clara, Calif.

"Scream louder for them than you've screamed for me the entire night," Swift told the hyped-up crowd when introducing Fifth Harmony's Camila Cabello, Ally Brooke, Normani Hamilton, Dinah-Jane Hansen and Lauren Jauregui.

Swift also prefaced the dazzling performance by informing the audience that her shiny blue outfit had been loaned to her by a friend. "[She's] in one of the biggest and most successful groups in the world. They have one of the most powerful and loyal fanbases in the world," Swift said. "They also have one of the biggest smash hit singles in the country right now called 'Worth It.'"

As expected, the stadium went nuts. Swift fit right in with the Fifth Harmony girls, strutting her stuff throughout the dizzying song. "Worth It" is the group's third single from their debut album, Reflection.

Other surprise guests on Swift's ongoing 1989 tour have included Fetty Wap, Nick Jonas, The Weeknd and Lorde.

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