When Joel Silver calls, Hollywood's hottest celebrities come running ... and some of them in hats!

Silver's Memorial Day bash in Malibu proved to be the hot ticket over the weekend with celebrities like Tom Cruise, Courteney Cox, David Arquette, Sean Penn and Barbra Streisand in attendance.

Check out our massive gallery below to see who else was partying in the 'bu with Mr. Silver. See Gwen and Gavin leaving the shindig ... after the jump.