Prepare and bake cake according to package directions for a 9x13 cake. Allow cake to cool,then poke holes with a wooden spoon handle, you want the holes to be fairly big,making sure you poke all the way to the bottom of the cake.
In a bowl whisk together instant pudding and milk. Stir until all lumps are gone. let pudding set for about 5 minutes.Pour pudding over cooled cake, taking care to get it in the holes as much as possible.
Put the cake in the fridge for 2 to 3 hours. Spread on cool whip and sprinkle crushed oreos on top.