In a large microwave-safe bowl, melt butter on high for about 30 seconds. Add marshmallows; stir to coat. Microwave on high 30–40 seconds longer or until smooth. Stir in peanut butter. Add cereal; stir gently until coated. Press into a greased 16-by-9-inch pan.
In a small microwave-safe bowl, heat chocolate chips and shortening on 70 percent power for 45 seconds. Heat in 10- to 20-second intervals until melted; stir until smooth. Spread over cereal mixture. Cool completely.
Cut into 2 1/2 by 2-inch triangles, with a thin base on bottom of triangle for hat brim. Decorate with frosting, jimmies for the buckle and licorice for the brim.