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Katie Cassidy and Annie Ilonzeh embraced fall brights at a People StyleWatch and Guess denim party celebrating the magazine’s October issue at Palihouse in West Hollywood. Former Gossip Girl Cassidy will star in the new CW show,  Arrow, which premieres on October 10th. Click through to see Beyonce, Carly Rae Jepsen, and more stars at this week’s hottest parties.

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