-- It was the surprise of a lifetime.
"I saw an ENTERTAINER tonight! @justintimberlake #Justinrcredible," Brooks posted on Instagram, along with a video of the two singing Brooks' famed 1990 hit "Friends in Low Places.”
In the video, posted in its entirety on YouTube, Timberlake, 33, starts singing the song first, the crowd joins in next, then Brooks takes the stage and the crowd goes nuts.
"Hold on," Timberlake says after the second verse, before welcoming the legend onstage. "Something don't feel right."