Heat oven to 300°F. Line a 15x10x1-inch pan with cooking parchment paper. In large bowl, mix popcorn and cereal.
In 1-quart saucepan, melt butter over medium heat. Add sugar, corn syrup and gelatin; stir until blended. Heat to boiling, stirring constantly. Reduce heat to medium-low; simmer 5 minutes, stirring frequently, until sugar is dissolved.
Immediately pour hot sugar mixture over popcorn mixture; toss until completely coated. Spread coated popcorn mixture in pan.
Bake 15 minutes or until set. Spread on waxed paper to cool. Break into bite-size pieces. Store tightly covered at room temperature.