Preheat your oven to 350°F (175°C). Lightly grease your 9x13-inch baking dish or line it with parchment paper.
In a large mixing bowl, combine the chocolate cake mix, water, vegetable oil, and eggs. Beat the mixture on medium speed for about 2 minutes until smooth and evenly blended.
Pour the batter into the prepared baking dish, spreading it evenly. Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. Let cool for 10 minutes.
While the cake bakes, prepare the instant Oreo pudding by combining the pudding mix with 3 cups of milk. Whisk for about 2 minutes until thickened. Refrigerate.
Using a fork or skewer, poke holes all over the surface of the warm cake about 1 to 2 inches apart.
Slowly pour the prepared Oreo pudding over the cake, focusing on filling the holes. Use a spatula to spread the pudding evenly across the surface.
Spread the thawed whipped topping evenly over the pudding layer.
Sprinkle the crushed Oreos over the whipped topping, then arrange the whole Oreo cookies on top.
Refrigerate the cake for at least 2 to 3 hours or overnight to allow flavors to meld and pudding to set.
Slice the cake into squares and serve.