In a large pot over medium-low heat, melt the butter.
Add the marshmallows and 5 drops of orange food coloring, adding more as needed to reach your desired pumpkin pie color. Stir until the marshmallows are completely melted and smooth with no white streaks remaining. Remove from the heat.
Quickly stir in the Rice Krispie cereal until well-coated.
Spray two 9-inch pie pans with non-stick cooking spray. Divide the Rice Krispies mixture evenly between the pans, spreading and flattening it. Use a greased measuring cup to press the mixture down evenly.
Let the Rice Krispies set at room temperature for 1 hour. Once set, flip the pans onto a parchment-lined baking sheet. Flip the Rice Krispies back over, and cut into 8 pie slices per pan.
In a medium mixing bowl, beat the cream cheese with a hand mixer until light and fluffy. Add the vanilla, powdered sugar (one cup at a time), and milk. Continue to beat until a thick icing forms. Set aside ⅓ cup of the mixture in a small ziplock bag.
Add the peanut butter to the remaining cream cheese mixture and beat until well combined. Place this mixture in another ziplock bag.
Cut a small tip off the corner of the plain cream cheese bag and pipe a small dollop onto the center of each Rice Krispie slice. Then, cut a small tip off the peanut butter-cream cheese bag and pipe a crust-like swirl along the top edge of each slice. Serve and enjoy!