Preheat oven to 300Â°F. Line a jelly roll pan with foil or parchment. If using foil, spray lightly with non-stick spray and set aside. Spray extra large mixing bowl with non-stick spray.
Place popcorn in prepared bowl. Place butter and syrup in a sauce pan on medium heat. Stir until butter is melted. Add sugar and Jell-O and stir to combine.
Increase heat and bring to a boil. Then reduce heat so it just simmers. Continue simmering for 5 minutes. Immediately pour over popcorn in bowl. Mix right away and keep stirring so everything gets well coated. Spread mixture onto prepared pan and spread out evenly.
Put the pan in the oven and bake for 10 minutes. Remove the pan from the oven and let cool to room temperature. Break into pieces and enjoy!