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It was Halloween on the Upper East Side and what better way to celebrate a night of tricks and treats than at the opening of Chuck Bass’s (Ed Westwick) hot new club? For the star-studded bash, guests like Serena van der Woodsen (Blake Lively) and Blair Waldorf (Leighton Meester) stuck to the Speakeasy theme and channeled the roaring ’20s. But of course, each girl put her own sexy spin on her flapper-inspired look. Serena flashed her long legs in a silver sparkling Collette Dinnigan minidress paired with a diamond Jennifer Behr hair clip and Christian Louboutin Pumps. Blair, on the other hand, took a more authentic approach in a white, beaded fringe Alberta Ferretti frock topped with a black Suzanna Dai collar. We love a flapper costume for Halloween so if you still haven’t gotten yours, check out how to get Serena and Blair’s roaring ’20-chic for less. Shop their looks here.