Make cake mix according to package directions and bake in a well-greased 9x13-inch pan. Bake cake according to times on the back of the box.
When cake is finished, allow to cool for about 10 minutes, then poke holes all over cake (about 1-inch intervals) using a wooden spoon handle.
In a medium bowl, add milk to pudding mixture and whisk until most of the lumps are removed. There will be a few lumps in the pudding because of the Oreo pieces that are in the pudding.
Pour pudding mixture over cake making sure to aim for the holes.
Spread it out with a spoon and gently push down on the pudding to help get it into the holes.
Then put the cake in the refrigerator to allow it to cool completely. About an hour.
Spread whipped topping on top of pudding layer.
Once it is set, top with crushed Oreo cookies. Slice then serve.