You're chilling at your prom. It's alright. Music's fine. You know you look good. Sounds like the after party is gonna be cool. Whatever.

Wait, what just happened? Why is everyone screaming and freaking out? Oh, right.

Yeah, Justin Bieber crashed a prom in Chatsworth, California, on Saturday night and people freaked the f--- out as if... well, Justin Bieber crashed their prom.

Justin, who was reportedly headed to a studio next door to where the prom was being held, clearly had no problem with the ear-piercing reception he got from the Chatsworth Charter H.S. seniors.

And they were lovin' it too. Especially the prom queen, who got to dance with him.

Check out this detailed description of the mayhem from an attendee who claims she was one of the first people to spot JB (and grind oh him for, like, two seconds).

Sorry, dudes.