As Taylor Swift’s Reputation Stadium Tour keeps rolling on, so does her tradition of welcoming other A-list performers onstage for surprise appearances, and Saturday night’s show in Pasadena’s famed Rose Bowl Stadium did not disappoint.

Fans were thrilled when Swift’s pal Selena Gomez walked onstage to perform a duet of her song “Hands to Myself” that had the audience going wild.

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“I want to say thank you to my best friend of about 12 years, almost 13. And the reason why she has been one of my best friends is because this person has never, ever judged a single decision I’ve made,” Gomez told the crowd. “She’s always met me where I’ve been. She’s encouraged me when I’ve had nothing to be encouraged about. And I don’t know if I would be as strong as I am if I didn’t have you and your family because you changed my life.”

Added Gomez: “But honestly thank you from the bottom of my heart for supporting someone that I know that is the most beautiful, strong, independent woman I’ve ever met. So thank you for supporting my best friend.”

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Following the performance, Swift took to Instagram to share her gratitude with her longtime friend.

Gomez wasn’t the only star to make a surprise appearance during the concert; earlier in the evening, Troye Sivan — wearing a T-Swift t-shirt, no less — joined Swift for a duet of his new single “My, My, My”.

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Sivan had another surprise in store for fans at the show, revealing that his upcoming album “Bloom” was set to drop on Aug. 31.

Check out how fans in the Twitterverse responded to Sivan’s announcement of a new album on the way:

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Taylor Swift’s Star-Studded ‘Reputation’ Tour