Melt butter in a saucepan, add marshmallows and stir until melted and well combined.
Spray your spoon with cooking spray. Add rice krispies and 2 tbsp sprinkles to marshmallow mixture.
Stir to combine well.
Pour into your 13x9 inch pan and spread evenly, pressing down firmly with your spoon or your fingers.
Garnish top of Rice Krispie treats with about 12 marshmallow ghosts (evenly space for serving size and cutting) Sprinkle last 2 tbsp sprinkles over the top. Refrigerate for about 30 minutes to an hour.