Watch Taylor Swift Bring Out Little Mix, Joan Baez and Julia Roberts at 1989 Concert 

Taylor Swift performs during The 1989 Tour at Soldier Field on July 19, 2015 in Chicago.

Taylor Swift celebrated girl power at her back-to-back concerts at Levi\'s Stadium in Santa Clara, Calif., over the weekend.

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On Friday night (Aug. 14), Swift invited Fifth Harmony. on stage to perform their hit song "Worth It," and the following evening she brought out Little Mix to play their new single "Black Magic."

The massive stadium crowd loved it. "LITTLE MIX!! Love these girls!! They smashed it tonight in front of 50,000 screaming fans. Amazing," Swift tweeted after the show.

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Little Mix, meanwhile, was left in disbelief after the performance. "OMG cannot quite believe what\'s just happened, one of the best experiences in our little mix life ever!" the British act posted on Instagram.

OMG cannot quite believe what\'s just happened, one of the best experiences in our little mix life ever! Cannot thank Taylor enough for having us tonight, 60,000 incredible screaming swifties with a sprinkle of Black Magic, thank you for being so welcoming to us! We love you Taylor can\'t wait to catch up very soon! xx Little Mix xx

A photo posted by Little Mix (@littlemixofficial) on Aug 16, 2015 at 1:02am PDT

"Black Magic," from Little Mix\'s upcoming third album

, recently became the pop outfit\'s longest-running U.K. No. 1 single. The group is slated to perform at the Billboard Hot 100 Music Festival, to be held Aug. 22-23 at New York\'s Jones Beach.

Little Mix wasn\'t the only surprise guest on Saturday. Swift also invited legends Joan Baez and Julia Roberts to the stage during "Style." The beloved folk singer and Oscar-winning actress "danced it out to \'Style,\'" Swift tweeted. "These two women are my heroes. What an honor."

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

1989 Taylor Swift Featuring Kendrick Lamar

Radio Songs Aug 22, 2015 3 Bad Blood 1989 Taylor Swift Featuring Kendrick Lamar

The Official U.K. Singles Chart Aug 22, 2015 3 Black Magic Little Mix

Billboard Canadian Hot 100 Aug 22, 2015 99 Black Magic Little Mix

Billboard Twitter Top Tracks Aug 22, 2015 13 Black Magic Little Mix

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