The ?Baby? stud and his ?Monte Carlo? cutie waltzed in to the reception and posed for pictures with the bride and groom along with some of the guests.
"Last night at my cousin Jeanine's wedding reception, out of nowhere, Justin Bieber shows up while one of his songs was being karaoked by one of the wedding guests," said a source who posted the video on YouTube.
"He stated that he was driving by the reception in Malibu and heard a party and his song being sung, so he decided to check out the event and ended up making a celebrity appearance."