The next time you're at the karaoke machine, choose your song carefully -- you never know who might be listening.

That was the lesson learned by guests at a Malibu, California wedding last Friday, when none other than Justin Bieber and Selena Gomez dropped by. As it turns out, the star lovebirds were apparently driving past the reception when they heard someone singing Bieber's 'One Less Lonely Girl,' and decided to have a closer listen.

The result, as you might imagine, was an unforgettably surreal moment for the wedding guests, captured in the below YouTube clip, which shows Bieber posing for pictures while pandemonium erupts. As Bieber later described it in a tweet, "WEDDING CRASHERS last night. hahaha. too funny. crazy story."