Melt butter in large saucepan on low heat. Add marshmallows, constantly stirring, until melted and well blended.
Remove from heat. Add Rice Krispie cereal and candy corn, mix well.
Grease a 13x9 pan and press the mixture onto the bottom of the pan.
Allow to cool completely before cutting into bars.
Notes
If you prefer, you may melt the butter in the microwave. Add the marshmallows and toss to coat them with butter then microwave until the marshmallows are melted.
Recipe by It's Gravy, Baby! at http://itsgravybaby.com/2013/10/candy-corn-rice-krispie-treats/