Popsugar Entertainment Halloween Mary-Kate and Ashley Olsen Halloween Costumes 14 Mary-Kate and Ashley Costume Ideas That Are Double the Trouble For Halloween October 28, 2017 by Kelsie Gibson View On One Page Photo 6 of 15 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 6 Mary-Kate and Ashley, Two of a Kind What to wear: One of you should wear cargo pants and a t-shirt, and the other should wear a blouse and a skirt. Don't forget your '00s hairdo. How to act: Like polar opposites. Previous Next Start Slideshow HalloweenAshley OlsenMary-Kate OlsenNostalgiaHalloween CostumesPop Culture Halloween CostumesMoviesHalloween Costumes For Women