Leighton Meester was joined by Penn Badgley on the set of Gossip Girl this morning, along with some of their castmates, including newcomer Roxane Mesquida and returning actor Hugo Becker. Roxane's character will play Prince Louis's sister, and Blair Waldorf's new enemy, on the upcoming episodes of the show. She's not the only new face who will be appearing on the small-screen hit this year. Elizabeth Hurley has also signed on to play a media mogul named Diana Payne during the upcoming fifth season. Yesterday was the first time we've spotted the GG stars on set in a while, as Leighton went solo to shoot a few scenes, but the whole cast and crew will be hard at work over the Summer. Gossip Girl is set to premiere on Sept. 26 on the CW.