This site has some great easy diy costume ideas! cute costume, and love the added duckie headband! I would add a long sleeve white shirt and white leggings so it's less revealing, but other than that it's a cute idea!
DIY Bat Dress Pattern from EvaDress. *For Updated Links and an Expanded Post on Bat Dresses go here.*This is an advanced sewing project Inspired by the illustration Travestissement Chauve-Sourisin in La mode Illustrée, Journal de la Famille, 1887