Kardashian steps out for son Mason's second birthday in L.A. Plus: Sofia Vergara, Katy Perry, Justin Beiber and more

THE CAT'S 'MEOW'

After being named one of 2011's Most Fascinating People, Katy Perry beams while aboard a trolley Wednesday during the unveiling of her new perfume, Meow!, at The Grove shopping center in L.A.