Butter a 9x 13-inch baking dish.
Combine marshmallows, peanut butter, and butter in a pot over medium heat, stirring constantly until melted and combined.
Off heat, stir in cereal until evenly coated; press mixture into the prepared baking dish in an even layer.
Add chocolate chips and butterscotch chips to a saucepan over medium to medium-low heat, stirring until melted, smooth, and combined; spread chocolate-butterscotch mixture over top of cereal mixture.
Cool until top solidifies, then cut into bars to serve.
