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Mischa Barton

MELBOURNE, AUSTRALIA - NOVEMBER 06: Mischa Barton poses at the Emirates marquee at the Melbourne Cup at Flemington Racecourse on November 6, 2012 in Melbourne, Australia. (Photo by Don Arnold/WireImage)

What Were They Thinking?!

This week's worst-dressed crew includes Mischa Barton, Beyonce, and Britney. -- By Matt Whitfield, Yahoo! Staff