Moon Costumes offer Costumes, Masks and Accessories. Fast shipping, lowest price guaranteed. The world’s largest Halloween costumes selection online. Moon Costumes is a premier seller of a unique selction of adult and child halloween costumes, masks, hats, wigs and costume accessories. The catalog is easily searchable, and the shopping system is unique in that it offers bulletproof security for your credit information, operating at a higher standard than anyone else in the industry.