Combine popcorn and candy corn in a large bowl.
Melt 1/4 cup butter in a large saucepan over medium heat; stir in 1/4 teaspoon salt and (10-ounce) bag marshmallows. Reduce heat to low; cook for 7 minutes or until the marshmallows melt and the mixture is smooth, stirring frequently.
Pour marshmallow mixture over popcorn mixture, stirring to coat well. Lightly coat hands with cooking spray; shape popcorn mixture into 20 (2-inch) balls.