The Hills stars have a festive Cinco de Mayo in West Hollywood. Plus: Blake & Penn, Katie and more

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HAVING A BALL

Blake Lively and Penn Badgley (both in Ralph Lauren) stick together on-camera and off, attending the Nina Ricci afterparty following the Met's Costume Institute Gala Monday in New York. And while the Gossip Girl stars don't admit they're dating, Badgley told PEOPLE, "I think she's incredible. She's an amazing person and she's beautiful – so there's not a lot to dislike."

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