Midway through "Sidewalks," the Starboy cut featuring Lamar, the rapper elevated unannounced onto the stage to deliver his guest verse. Following that collaboration, Lamar hung around to perform his Damn. track "Humble" solo on the Forum stage.
The surprise appearance marked the second time the two artists delivered their Starboy song together: In December, the Weeknd and Lamar staged the debut performance of "Sidewalks" at a small venue, Vevo-sponsored concert in Los Angeles.
"He's a genius," the Weeknd previously said of Lamar. "He did it there on the spot. He'd walk around, he'd play the record over and over again… He's writing his verse in his head… He was really committing, he really put his all into it. It wasn't just a random Kendrick Lamar verse. It was something special."
The Weeknd will once again perform at Inglewood, California's the Forum Sunday night.