Combine powdered gelatin with applesauce. Place four whole-graham-cracker sheets, lengthwise and touching, in a single layer in a serving dish. Using a rubber spatula, spread a heaping 1/2 cup of applesauce mixture over the crackers. Repeat layers five times. Frost with whipped topping. Chill in refrigerator overnight and slice crosswise to serve.
Optional: Reserve a teaspoon of powdered gelatin to sprinkle over whipped topping before chilling.