Taylor Swift surprises super-fan with 'King of My Heart' serenade at engagement party

Taylor Swift made a super-fan's engagement party extra-special.

“There was a person who is not here, who sort of played a part in all of this,” Alex Goldschmidt announced in a video posted to Instagram. “So I would like to welcome — and if you could give a warm welcome to — my friend Taylor.”

Swift, 29, clad in a blue dress, ponytail and her signature red lip, emerged holding a guitar.

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“Alex emailed me and said he was going to do this, that there was a song that was really special for you, too, called ‘King of My Heart,'” Swift said.

“So I’ve come prepared,” she added, motioning to her guitar. “I’ve been off tour for a while, but hopefully it’s alright. This is from Alex but sung by me.”

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Goldschmidt, 30, revealed on Instagram, “I decided to propose to Ross listening to this song in my car.  I can’t thank Taylor enough for wanting to help make this day so special. #RossAndAlexForever.”

The festivities were held at the Sycamore Tavern in Los Angeles.

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Goldschmidt later tweeted, "I have never felt so overwhelmed with love and exhaustion in my life. Thank you for all the messages. I can’t possibly respond to them all, but know that your love and support means the world to me. And holy s—t, Taylor Swift is an angel who gives the best gifts."