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Fashion's Night Out is like Halloween for the style set; They get dressed up in their hottest duds and go from store-to-store looking for the most entertaining, star-studded bashes.

And Thursday night was no exception, with huge crowds turning out across the country to shop and party alongside their favorite A-listers.

Sarah Jessica Parker made the rounds in New York City, autographing shoes at Manolo Blahnik, getting serenaded by Oscar de la Renta at his Madison Avenue store and ending her evening at the Fred Leighton boutique. The style icon sported a black leather Prabal Gurung dress with a pleated skirt, belt and white Manolo Blahnik heels.

Also in the Big Apple, Hayden Panettiere helped unveil Stuart Weitzman's Young Hollywood Cares Collection for Ovarian Cancer Research. The actress wowed in a plunging Fendi jumpsuit with ruffle detail and black ankle boots that she co-designed for the philanthropic shoe line.

On the West Coast, Rachel Bilson stopped at Sunglass Hut clad in a a Vanessa Bruno skirt and blazer, ALC tank, Luv AJ headpiece, and accessorized with Chloe wedges and a Phillip Lim bag, while Nicole Richie hosted the festivities at the Beverly Center in a boho-chic purple maxi dress by her own Winter Kate line and a sparkling headband.

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