Butter a 9" x 13" casserole dish.
In a large pot over low-medium heat, melt the butter.
Add the marshmallows and stir until smooth.
Pour in the rice krispie cereal and, with a spatula, stir until the cereal is evenly coated with marshmallows.
Spoon the mixture into the prepared casserole dish and press until the rice krispies fill the dish and the top is flat.
Allow to set for 30 minutes.
Remove the cooled rice krispie treats from the dish and cut into rectangles of various sizes.
Place a bowl over a small pot of boiling water and add the green candy melts to it.
Stir until melted. If the chocolate is too thick for dipping, adding a teaspoon of vegetable shortening.
Dip the top of each rice krispie treat into the green candy melts and then into the black jimmies sprinkles.
Add two royal icing eyes.
In a small bowl, melt the black candy melts in the microwave using 10 - 15 second increments.
Pour into a piping bag and pipe stitches onto the treats.
Allow to set completely before packaging.