Decorate cake. Prepare buttercream icing following recipe directions. Tint portions violet/rose combination (for violet) and black. Use spatula and black icing to Use spatula to ice inside of mouth and nose smooth.
Use tip 16 and violet icing to cover cake with stars. Use full strength white Color Flow icing to attach white cookies to violet cookies; position on cake. Use tip 2A and black icing to pipe dot pupils and outline eyebrows.
Position five candy worms in mouth. For hair, use food-safe scissors to cut licorice pieces to 3 in. Insert in cake side, leaving 1 1/2 in. extended.