Niall Horan Joins Taylor Swift on Her "Reputation" Tour in London

These surprises keep getting better and better.

The surprises for Swifties attending Taylor Swift's Reputation world tour just keep coming. After bringing besties including Selena Gomez, Troye Sivan and Shawn Mendes to the stage during past performances, the singer was joined by Niall Horan during her Friday (June 22) show in London.

The former One Direction member appeared with Taylor for a performance of his song "Slow Hands," as noted by Just Jared Jr. Following their surprise duet, Taylor shared a number of behind the scenes images from their soundcheck on Instagram, writing, "Soundcheck at Wembley Stadium with this guy @niallhoran THANK YOU for surprising the crowd tonight!!!" Niall also shared his appreciation for the invitation, 'gramming of a picture of the pair hugging on stage with the caption, "Thank you @taylorswift for having me last night at Wembley . What a fantastic experience to share the stage with you!"

Fans who were lucky enough to be in attendance for the surprise shared their own videos and pics to social media. One fan crowned it "THE BEST SHOW," while another called it "iconic." According to one fan's account of the evening, Taylor joked a bit with the crowd before bringing Niall on stage and called him "a pro."

There's no word on who may join Taylor next on stage, but U.S. fans may want to hurry up and buy their tickets. The singer officially arrives back in the United States on June 30, with a performance in Louisville, Kentucky.

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