Taylor Swift is throwing back to Red-era self again by popping up in unexpected places. The superstar surprised lucky fans at their engagement party over the weekend with an acoustic performance of "King of My Heart."

Alex Goldschmidt had proposed to his boyfriend earlier in the day, but that wasn't his only surprise. Alex then brought his fiance, Ross, to a party with their closest friends — including his buddy Swift.

"Alex emailed me and said he was gonna do this and that there was a song really special to you two called 'King of My Heart,'" Swift remarked when she made her entrance, "So I’ve come prepared. I've been off tour for a while, but hopefully it's still alright. This is from Alex. It's sung by me, but it's from Alex."

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She then performed an acoustic rendition of "King of My Heart" from her latest album, Reputation.

The once-country star took the time to meet the couple's friends and family members, posing for pictures with them. In an interview with Buzzfeed, Goldschmidt reveals he only reached out to Swift two months earlier to thank her for the song and tell her how special it was to him and his then-boyfriend. It was only later that her publicist reached out to ask if Swift could be a part of their special day.

You may recognize Goldschmidt from his popular social media accounts, talking about everything Swift and entertainment, or you may recognize him from his appearance in Swift's "Shake It Off" music video, for which she hand-selected fans to join in a dance sequence.

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