Line your baking pan with parchment paper or a silicone mat and set aside. Measure out all ingredients so you're ready to go.
Bring a large saucepan over medium heat and melt the butter, listening for it to sizzle softly as it melts completely.
Add the marshmallows to the melted butter, stirring continuously until they melt into a smooth, glossy mixture. The smell of sweet, toasted marshmallows will fill the air.
Stir in the pumpkin spice and canned pumpkin until well combined, creating a fragrant, orange-tinted sauce that coats the marshmallow mixture.
Remove the saucepan from heat and immediately pour in the Rice Krispies, folding gently with a spatula until all the cereal is coated with the pumpkin-spiced marshmallow mixture.
Transfer the mixture into your prepared pan, pressing down firmly with a spatula or wax paper to evenly distribute and create a compact layer. The mixture should be sticky but manageable.
Allow the treats to cool at room temperature for about 15-20 minutes, until they set firm and become easier to cut.
Once cooled, lift the treats from the pan using the parchment paper and cut into fun Halloween shapes or squares with a sharp knife.
Arrange the cut treats on a serving platter and enjoy their crunchy, gooey texture, enhanced by seasonal pumpkin and spice aromas.
