Prepare cake according to box instructions and make two layers using 6-inch round pans. Bake and cool on cooling grid.
Prepare Spring Green icing using this color tint formula from the Color Right Performance Color System: 4 cups icing + 30 Y + 6 B. Stack layers on cake plate for a two-layer cake, using leveler as needed. Ice cake sides smooth with green icing.
Use black pouch icing without tip to cover top of cake. Use tip of spatula to create spiral effect. Use black pouch icing with star tip to pipe pull-out bangs around top edge and two hair strands on cake top.
Prepare a disposable decorating bag with green icing; cut a hole in point of bag the size of tip 3. Attach candy eyeballs with dots of green icing. Pipe green eyelid.
Use black pouch icing with round tip to pipe dot nose and neck bolts, outline mouth and stitches.