Make cupcakes. Prepare batter following recipe directions. Bake and cool cupcakes.
Ice cupcakes. Prepare chocolate buttercream and white buttercream icing, separately, following recipe directions. Use spatula and chocolate icing to ice top of cupcakes smooth.
Decorate cupcakes. Insert skull icing decorations in top of cupcakes toward the edge of the baking cup. Use tip 4, cut disposable decorating bag with coupler and white icing to pipe shoulder and arm sections on top of cupcakes. Use tip 3 and icing to pipe fingers. Sprinkle crushed sandwich cookies around on tops of cupcakes.