Chris Brown's "Party Tour" is well underway, and Anaheim fans were hit with a big surprise. Around halfway through the show, Chris Brown introduced the DAMN. rapper before Kendrick Lamar emerged from backstage to grace the lucky audience with a performance of "Humble." A fan-captured Instagram videos show Kendrick holding it down while Chris dances alongside him, all while the stadium explodes with energy. 

Chris posted a few pictures of the performance on his Instagram, including one where the singer seems to bow in a gesture of honor.