1Heat oven to 350°F. Place paper baking cup in each of 24 regular-size muffin cups or spray with cooking spray. Make and bake cake mix as directed on box for cupcakes, using water, oil and eggs. Cool 10 minutes; remove from pans to cooling racks. Cool completely, about 30 minutes.
2In large bowl, beat butter and shortening with electric mixer on medium speed 2 minutes or until creamy. Slowly beat in powdered sugar and vanilla. Mound about 2 tablespoons frosting on each cupcake. Using fingers, make deep indentations in sides of frosting to look like skull.
3Place 2 chocolate candies on each cupcake for eyes. Cut remaining chocolate candies in half; attach for nose with cut sides in frosting. With dampened kitchen scissors, cut each marshmallow into 5 slices; arrange slices on cupcakes to look like teeth.