It's two weeks and counting to your sister's wedding. With all the frenzy over her dress, you haven't thought for a second about yours. Let the couture design trio at Menage a Trois be fairy godmothers to your frantic Cinderella. Looks start at $750, and range from dupioni-silk dinner suits fit for Le Cirque to smooth-as-glass boot-cut leather pants for downtown divas. But the best part is that the staff works at warp speed. An iridescent silk-taffeta ball gown or bias-cut chiffon slip-dress, with one muslin and two regular fittings, takes two weeks. In a pinch, they can even turn a panicked phone order on Wednesday morning into a simple, perfectly fitted sheath by Friday afternoon. The shop's helpful owners know the ins and outs of frantic partygoing -- they'll track down the perfect Sergio Rossis, send you for an updo, and book dinner at the Brasserie without batting an eye.