Lightly grease a 9-inch round pie dish with nonstick cooking spray to prevent the treats from sticking.
In a large saucepan over low heat, melt the butter and mini marshmallows together. Stir continuously until the mixture is completely melted and smooth.
In a large saucepan over low heat, melt the butter and mini marshmallows together. Stir continuously until the mixture is completely melted and smooth.
Remove the saucepan from the heat. Add the Rice Krispies cereal and gently mix until all the cereal is evenly coated in the marshmallow mixture.
Set aside approximately 2 cups of the Rice Krispie mixture. Press this portion around the outer edge of the prepared pie dish, creating a crust about 1½ inches wide. Leave the center open for the pumpkin-colored filling.
Add the orange gel food coloring to the remaining Rice Krispie mixture and stir until the color is evenly distributed. Spoon the orange mixture into the center of the pie dish, gently pressing it into place so it fits snugly against the crust.
Allow the Rice Krispie pie to cool and firm up for approximately 30 minutes. Once set, cut into wedges just like a traditional pumpkin pie. Top each slice with a dollop of whipped cream and some pumpkin spice (if you want)