Butter a large mixing bowl and set aside. In a large saucepan, melt the butter over medium heat, until it begins to bubble softly with a fragrant aroma.
Add the mini marshmallows to the melted butter and stir continuously until completely melted and smooth, creating a glossy mixture.
Remove the saucepan from heat and stir in the warm spices such as cinnamon and nutmeg, mixing until evenly incorporated.
Divide a few drops of orange food coloring into the marshmallow mixture and stir well to achieve a vibrant pumpkin-orange hue.
Pour the colored marshmallow mixture into the prepared mixing bowl, then add the rice cereal gradually, folding gently with a spatula until evenly coated and sticky.
While still warm, scoop out portions of the mixture and shape them into small pumpkin-like spheres or use a cookie scoop for consistency.
Place the shaped treats onto a sheet of parchment paper and use your hands or a mini cookie scoop to gently form into rounded pumpkin shapes.
Let the treats cool and set at room temperature for about 15 minutes so they firm up slightly.
Optionally, add small stems or leaves made from green fondant or icing for added decoration.
Serve the pumpkin-shaped rice Krispie treats at room temperature, enjoying their crunchy exterior and soft, sticky interior with autumnal flavors.
