Preheat the oven to 350 degrees F. Spray a 9-x-13-inch cake pan with cooking spray and set aside.
Prepare the cake mix according to box instructions. Pour batter into the prepared pan and bake according to package directions. Allow to cool for 10 minutes.
While the cake is cooling, make the pudding. In a small bowl, whisk together pudding packets and milk until thickened.
Using the end of a wooden spoon, poke holes all over the cake. Spread pudding mixture on top and top, then layer with ⅔ of the banana slices. Cover with plastic wrap and refrigerate at least 30 minutes.
Spread whipped cream on top, then garnish with and sprinkle all over with vanilla wafers and remaining banana slices.
Use a 9×13 inch pan for this poke cake recipe.
Make sure the cake is fully cooled before adding the cream topping.