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.

“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.”

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.

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."