By Bronwyn Barnes
Updated Jul 12, 2011 @ 5:30 pm
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Ryan Miller/Getty Images

Lauren Conrad (in Paper Crown) and BFF Lo Bosworth were pretty in pink frocks when they attended the Dinosaur Ball in Los Angeles. "Go to the L.A. Natural History Museum to see the new T. Rex!" Lo tweeted post-party. Click through the gallery to see Emma Watson, Sarah Jessica Parker, Katie Holmes and more stars at yesterday's hottest parties!