Heat oven to 375°F. Place paper baking cup in each of 24 regular-size muffin cups. Make and bake cake mix as directed on box for cupcakes. Cool 10 minutes; remove from pans to cooling racks. Cool completely, about 30 minutes. Frost cupcakes with frosting. Sprinkle with colored sugar. Place eyeball(s) or zombie treat on top of each cupcake.