From Julianne Hough's 'Crazy Eyes' blunder to Matt Lauer's terrifying Pam Anderson, these are some of the worst celebrity Halloween costume offenses ever committed.
The 'American Idol' finale celebrated the conclusion of its 13th season by inviting big stars onto its stage to perform alongside the former contestants and two finalists. Check out performances by Demi Lovato, Paramore, Phillip Phillips and more.