Taylor Swift's 'Bad Blood' Co-Stars Cara Delevingne & Mariska Hartigay Join Her On-Stage in Phildelphia

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Taylor Swift is showing off her beautiful BFFs -- again!

During last night's Philadelphia stop of her 1989 tour, Taylor brought her "Bad Blood" co-stars Cara Delevingne and Mariska Hargitay on stage to recreate a little of their music video magic. 

Even Taylor couldn't believe the star-studded evening she had.

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Apparently "Bad Blood" love runs deep -- just two weeks ago, models Martha Hunt and Gigi Hadid strutted their stuff at Taylor's show in Detroit.

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Taylor is known for surprising fans with appearances from famous friends as well as live collaborations with other artists, so it's no surprise that Cara and Mariska weren't the only two familiar faces who popped up in Philly. The 25-year-old singer was also joined in the City of Brotherly Love by Echosmith for a rendition of the band's hit song "Cool Kids."

Echosmith's lead singer Sydney Sierota was pretty stoked about the drop-in herself.

Solid night of surprises, Taylor!

If you couldn't make it to Philly, don't worry -- you can relive the fierce "Bad Blood" video below.