For our daughter’s fourth birthday, we threw a Batgirl birthday party. This 4 year old birthday party theme wouldn't be complete without DIY superhero cape for kids, batgirl cookies, and a balloon garland along with other batgirl birthday party ideas. Looking for 4th birthday party themes, batgirl birthday party decorations, birthday decorations, or birthday decoration ideas? Check out this post on a superhero birthday party. Our daughter loved this fourth birthday girl theme for her party.