Preheat the oven to 350°F and grease a 9 x 13-inch baking pan.
In a large mixing bowl or the bowl of a stand mixer, combine the cake mix, water, oil and eggs. Beat on medium speed for about two minutes. Pour the batter into the prepared baking pan.
13.25 ounce chocolate cake mix, 1 cup water, ½ cup vegetable oil, 3 large eggs
Bake the cake for 30 to 35 minutes, or until you can insert a toothpick into the center and it comes out mostly clean (a few moist crumbs is great).
Poke holes all over the cake using the handle of a wooden spoon or a large straw.
In a large liquid measuring cup, whisk together the milk and instant pudding mix. Quickly pour the pudding mixture over the top of the cake, ensuring you fill all the holes. Place the cake in the refrigerator for one hour to allow the pudding to set.
2 cups whole milk, 3.4 ounces instant vanilla pudding mix
In a small mixing bowl, combine the Cool Whip and ½ cup of the crushed Oreos. Spread the Cool Whip over the top of the cake, sprinkle it with the remaining crushed Oreos, and enjoy.
8 ounces cool whip, 1 ½ cups crushed Oreos