OMG! GOSSIP GIRL HITS 100 EPISODES! — The much-anticipated 100th episode will open with a musical dream sequence featuring Serena (Blake Lively), Blair (Leighton Meester) and all the men in their lives (Penn Badgley, Chace Crawford, Ed Westwick and Hugo Becker). Also, while Chuck (Ed Westwick) wrestles with the reality that Blair is about to walk down the aisle with Prince Louis (guest star Hugo Becker), the return of Georgina Sparks (guest star Michelle Trachtenberg) might make the royal affair a royal disaster. Kelly Rutherford and Matthew Settle also star. Mark Piznarski directed the episode written by executive producer Joshua Safran.