Preheat the oven to 375 degrees and spray a 9x13 baking dish with non-stick cooking spray.
In a small mixing bowl, combine crushed Oreos and melted butter. Mix well until all of the Oreo mix is damp and has the consistency of wet sand.
Pour crumb mixer into the bottom of the baking dish and press flat with the palms of your hands. Be sure to press firmly and evenly into the corners and edges.
Bake for 6-7 minutes. When done, allow to cool before use.
In a medium mixing bowl, combine cream cheese and powdered sugar together using an electric hand or stand mixer. Mix for 1-2 minutes until fully blended.
Add 8oz whipped topping and continue to mix. When done, set aside.
In a separate mixing bowl, combine cake mix, pudding, and milk. Mix together on low to medium speed for about 2 minutes or until the pudding begins to slightly thicken.
Add the rainbow sprinkles to the mixture, reserving a handful for garnishing the top of the cake. Mix well until the sprinkles are evenly distributed.
Pour cream cheese mixture over the completely cooled crust and spread evenly using a rubber spatula.
Top with pudding mixture, spreading evenly.
Finally, top with the rest of your whipped topping and spread evenly creating a smooth and flat surface.
Sprinkle with rainbow sprinkles and place inside the refrigerator to chill for at least 4 hours or overnight before serving.