Preheat oven to 250º F. Line a baking sheet with waxed paper or foil; set aside. Spray a large bowl with cooking spray (to reduce sticking) and place popcorn inside; set aside. Heat butter, corn syrup and sugar in a small saucepan over medium-low heat, stirring to blend. When butter is melted, stir in gelatin until completely dissolved. Bring mixture to a boil. Reduce heat to low and simmer 5 minutes, stirring frequently. Immediately pour hot mixture over popcorn and stir to coat completely. Spread onto prepared baking sheet and sprinkle with sugar sprinkles, if desired. Bake 12 minutes; cool in pan. Break into small pieces to serve. To store: place in an airtight container.