Place popcorn (make sure to remove unpopped kernels) in large bowl; spray lightly with cooking spray.
In large saucepan, combine butter, confectioner sugar, marshmallows and water. Stir until mixture is melted and blended. Add pumpkin pie spice and food coloring, mixing well.
Pour mixture over popcorn, stirring until well coated. Add pumpkin seeds; stir to coat.
Shape 1/4 cup of mixture into oval. Add decorations to look like “pumpkin heads”.