Rihanna attended the launch of her River Island fashion collaboration wearing a head-scratching outfit that featured two jeans layered on top of each other. Sadly, the "Diamonds" singer is not the first (nor the last) celebrity to commit a serious crime against denim. From Justin Bieber's acid washed nightmare, to Britney Spears and Justin Timberlake's matching ensembles, check out this gallery of stars who should have just said NO to jeans.