In S01E01 of Castle, Rick is playing poker with other (real life) authors:
Going by Wikia, the guy with the glasses is James Patterson. The chap on the right is Stephen J. Cannell (and the one with his back to the camera is Rick himself). Who's the lady on the left and who's the blonde (that I don't remember seeing)?
EXTERNAL EDIT: Here's a better picture of the brunette. She's definitely the dealer.