Watch Justin Bieber throw a superfan the best quinceañera

Pop idol Justin Bieber never stops surprising his fans.

This time, the singer showed up at the door of superfan Ashley for her quinceañera as part of Fox's show "Knock Knock Live." The girl wasn't able to celebrate her 16th birthday due to a meningitis diagnosis, but Justin made her day.

Here is the video of him showing up at the door:

And here is a gallery with some Bieber overload:

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