As all music festivals do, Ultra Music Festival's last night ended with a bang.

Skrillex was the last performer of the three-day event. He had hundreds of thousands of fans headbanging their brain cells into obscurity as he played his signature, bass-heavy anthems. Arguably, he was the most anticipated headliner.

Judging from his past performances, such as his B2B with Kaskade on Holy Ship!, Skrillex is no stranger to giving his audience the unexpected. Halfway through his set, both the festival crowd and online viewers were in for a marvelous surprise as Skrillex's counterpart Diplo stood front-and-center, waving around a Jack Ü flag. The duo continued to perform their new hits together until close, finishing off with "Where Are U Now." Another surprise then took place: Justin Bieber danced to centerstage to sing his part.

Other surprise guests included P. Diddy, Kiesza, and CL, with whom Jack Ü collaborated on "Dirty Vibe."