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Allison Williams

NEW YORK, NY - NOVEMBER 26: Actress Allison Williams attends the 22nd Annual Gotham Independent Film Awards at Cipriani Wall Street on November 26, 2012 in New York City. (Photo by Jamie McCarthy/WireImage)

What Were They Thinking?!

This week's worst-dressed crew includes Kristen Stewart, Kanye West, and Katy Perry. -- By Matt Whitfield, Yahoo! Staff