After months of searching, it looks like Serena has finally found her father. Sources say that actor William Baldwin has joined the cast of 'Gossip Girl' as William van der Woodsen, Serena's elusive dad who has been M.I.A. for the show's entire duration. Baldwin's gig will reportedly last for three episodes and will kick off sometime in April. Now that's something to gossip about. [Ausiello Files]