In a large microwave safe bowl, heat the butter in the microwave until melted. Stir in the marshmallows, coating them with the butter, then microwave on high for one minute, or until melted. Stir in the Rice Krispies until well blended. Add the mini marshmallows and sprinkles, then stir to combine. Pat the mixture into a greased 9 x 13 pan, then top with the Peeps bunnies. Let set for 20-30 minutes before slicing and serving.