Dempsey makes a front-row appearance at Timberlake's fashion debut. Plus: Cameron Diaz, Nicky Hilton and more.

IN THE KNOW

Patrick Dempsey gets with the program at the unveiling of Justin Timberlake's new clothing line, William Rast, at L.A.'s Social Hollywood on Tuesday. The Grey's Anatomy star rocked a very McDreamy ensemble of his own – a tie-and-cardigan combo.