Report CardFrom Naomi Watts to Justin Bieber, This Week's Best and Worst DressedMisty White Sidell03.08.13Report CardFrom Naomi Watts to Justin Bieber, This Week's Best and Worst DressedTilda Swinton’s classic perfection, a Vogue editor’s Chihuahua works, and Kate Moss’s sparkling Hedi Slimane debacle. See the fashion highs and lows of the week.Misty White Sidell03.08.13 9:45 AM ETGettyWhile style stars preened in the front rows at Paris Fashion Week looking pitch-perfect, there were some misses across the Channel in London. See this week’s best and worst dressed. Pascal Le Segretain/GettyBest Dressed Minimalist: Naomi WattsOn the last day of Paris Fashion Week, Naomi Watts sat front row at the Louis Vuitton show, wearing a coat and dress from the brand’s spring 2013 collection. Watts rounded out her outfit with a simple pair of black pumps and Vuitton’s Alma bag in a light mint green Pascal Le Segretain/GettyBest Dressed Winter White: Tilda SwintonTilda Swinton turned up to Pringle of Scotland’s archival fashion event in Paris on Tuesday—in a dress she co-designed with the classic brand. The white column “interpreted a Grecian gown worn by [Grace] Kelly.” reported WWD. Pascal Le Segretain/GettyBest Dressed Lady in Red: Giovanna BattagliaFashion editor and street-style star Giovanna Battaglia wore this laminated red coat and bow heels to Chanel’s fall 2013 show on Tuesday. Adding some extra panache, she accessorized the ensemble with a sleek pair of sunglasses and a studded clutch. Marc Piasecki/GettyBest Dressed Hands: Anna Dello RussoVogue Nippon Editor-at-Large Anna Dello Russo loves creating a spectacle with fashion. But she reached new heights at Valentino’s show: she showed up with a dressed-up Chihuahua in one hand, and a miniature Hermès Birkin bag in the other. Her printed suit rounded out the eyeful ensemble. Pascal Le Segretain/GettyBest Dressed in Pajamas: Marc JacobsDuring New York Fashion Week, Marc Jacobs closed both of his shows in pajama suits, one plaid, the other eggplant silk. Fast-forward almost three weeks to his Louis Vuitton show, and Jacobs emerged in PJs once again, this time in an elaborate print featuring flowers and little owl cartoons. Venturelli/GettyBest Dressed Black on Black: Carine RoitfeldIt serves Carine Roitfeld right to turn up to her own party looking better than anyone else. And that’s exactly what she did at the launch of the second issue of her CR Fashion Book. The editor wore a black dress with sheer black hosiery and black lace-up heels to celebrate her newest creation. Venturelli/GettyWorst Dressed Fishnets: Kate MossKate Moss was the first person to step out in Hedi Slimane’s second collection for Saint Laurent Paris. The supermodel, who walked in Louis Vuitton’s show on Wednesday, turned up to Carine Roitfeld’s CR Fashion Book party the night before in Slimane’s sparkling tights, minidress, and blazer. Dominique Charriau/GettyWorst Dressed, Thigh Mesh: Jessica ChastainJessica Chastain usually gets it right. But when Givenchy dressed her to sit front-row at its fall 2013 show, the Oscar-nominated actress fell apart. Her flat-ironed hair, unflattering outfit, and uncomfortable stance sunk the classic Hollywood look that she’s best known for. FameFlynetWorst Dressed Legal: Justin BieberJustin Bieber may have turned 19 this week, making him legal in his native Canada, but his clothes aren’t reflecting his newfound adult status. The pop star went for a walk in London in a pair of drop-crotch, pastel leopard pants, a printed shirt, and a studded baseball cap. Dave M. Benett/GettyWorst Dressed, Double Dipping: RihannaRihanna celebrated the launch of her River Island collection in London wearing a pair of the line’s layered jeans. While the style isn’t exactly flattering, it also seems incredibly difficult to put on.