Every time Justin Timberlake and pal Jimmy Fallon get together we're on the floor laughing, and yesterday they kicked things up a notch when they shook their moneymakers to Beyonce's "Single Ladies" at the U.S. Open. LOL!

The duo were sitting in the Emirates Suite watching Roger Federer play Richard Gasquet, and as soon as they saw themselves on the jumbotron, they started busting moves to Bey's hit song. JT seemed a little bit more into it than Jimmy, but we certainly appreciate the effort.

Timberlake and Fallon reunited on The Tonight Show later in the evening, and they teamed up for another hilarious installment of History of Rap. Loves it!