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 11 of 15 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 11 Mary-Kate and Ashley, The Adventures of Mary-Kate & Ashley What to wear: A gray trench coat, a matching fedora hat, and cool shades. How to act: Like you're on a mission to solve a mystery. Previous Next Start Slideshow HalloweenAshley OlsenMary-Kate OlsenNostalgiaHalloween CostumesPop Culture Halloween CostumesMoviesHalloween Costumes For Women