To make the cake layer, start by preheating the oven to 350 degrees. Spray a 13×9 inch baking dish with non-stick spray. Combine cake mix, pumpkin puree, and water in a large bowl. Mix until well combined, and transfer into the baking dish. Bake for 25-30 minutes, or until a toothpick comes out clean. When completely cooled, cut into small squares and set aside.
While cake is baking, in a large bowl, mix everything except for Tru Whip and gingersnaps together using a hand held electric mixer (or kitchen aid mixer), scraping down the sides and beating everything together until smooth and creamy. Fold in Tru Whip gently with a spatula.
In a trifle bowl or (a large pretty glass serving bowl), layer half of the cake, half of the creamy pumpkin mixture, and half of the gingersnaps. Repeat layers until the trifle glass is filled to the top, ending with the creamy pumpkin mixture.
Garnish with additional crushed gingersnaps if desired, (or butterscotch chips). Refrigerate for at least one hour, or up to 2 days before serving. Enjoy!