In a large pot, melt the butter over medium-low heat. Once it's melted, add the marshmallows and about 5-10 drops of orange food coloring. Stir until the marshmallows are completely melted and you get a lovely pumpkin color. Turn off the heat.
Stir in the Rice Krispies quickly until they’re fully coated. Spray two 9-inch pie pans with non-stick cooking spray.
Divide the mixture evenly between the pans, pressing it down and smoothing it out. Use the bottom of a measuring cup sprayed with cooking spray to help press the mixture evenly. Let them set on the counter for about an hour.
After an hour, flip the pans upside down onto a baking sheet lined with parchment paper. Gently remove the Rice Krispies from the pans, flip them right side up, and slice into pie-shaped pieces—about 8 slices per pan.
In a medium bowl, beat the cream cheese with a hand mixer until fluffy. Gradually add the vanilla, powdered sugar (one cup at a time), and milk, beating until you get a thick icing.
Transfer 1/3 cup of this mixture into a small zip-top bag and set it aside. Mix the peanut butter into the remaining cream cheese mixture, then transfer it to another small zip-top bag.
Cut a small tip off the corner of the bag with the cream cheese mixture and pipe a dollop onto the center of each Rice Krispies slice. Use the peanut butter mixture bag to pipe a swirl or "crust" on top of each slice.