Make the cupcakes according to the directions on the cake mix box. (See note above for what else you might need to make cupcakes with a box mix.)
Once the cupcakes are done baking, set them aside to cool completely, about 45 minutes or overnight. If making in advance, cool completely on a wire rack then store covered in an airtight container until ready to decorate up to two days in advance.
Ice only the tops (not the sides) of all the cupcakes with the green frosting about ½-inch thick.
Press the broad side of the candy corns into the icing over half the tops (white part pointing up) as the hair.
Gently add candy eyeballs for eyes. See photos.
Keep extras covered in an airtight container for up to three days.
Notes
If your store doesn’t have green vanilla frosting, you can use food coloring and white icing to create the color yourself.