Alicia Keys brought her Set the World on Fire tour to Los Angeles Tuesday (March 13) and surprised concertgoers by bringing Compton rhyme-slinger Kendrick Lamar to the stage.

In a YouTube video recorded by a fan who was at the show, Keys sets the mood by singing Janet Jackson's verse from the ballad 'Anytime, Anyplace.' Of course, as you may know, K.Dot samples the tune on his latest single, 'Poetic Justice.'

After she sang the verse, on cue, Lamar jumps out onstage to perform the song, much to the fans delight. According to VIBE, the TDE artist then finished his set with his chart-topping hit, 'Swimming Pools (Drank).'

It's been a good week for both of these talented superstars. Keys just launched her tour, which also features Miguel, and is encouraging fans to participate in the Your City, Your Video project with Blackberry.

Meanwhile, Lamar was crowned the "Hottest MC" last week by MTV and is about to headline several music festivals this summer with his Black Hippy crew.

Watch Kendrick Lamar's 'Poetic Justice' Video