Santa's Littlest Worker 12/24/2007 2:47 PM PST BY TMZ STAFF Someone's got the elfin spirit. Fashion slave celebutwin Mary-Kate Olsen was spotted on Fairfax Ave. in Los Angeles, buying either Christmas gifts or her supply of jewelry for the week. Her outfit's not too bad either-- because it's mostly hidden. See Also Yakkity-Yak, Olsen's Back! PETA to Olsens: Pelt You!