According to The Daily Mail, Harry surprised Olivia Mckee, the daughter of a millionaire businessman, while she was celebrating her b-day with about one hundred friends at Manchester's Great John Street Hotel.
Not only did Harry sing her "Happy Birthday" alongside her pals, he snapped pics with her and chatted it up too.
Olivia was quick to brag to other 1D fans on Twitter by posting, "Harry styles came to my 18th bitchez," and "Oh my god he kissed me."
She even thanked him personally, "@Harry_Styles thank you so much to coming to my 18th xxxxx."
We can't even imagine how much her dad dished out for that surprise!
What would you do if Harry showed up at your party?!
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Gallery | Harry Styles' Single Style