Preheat oven to 325° and spray a 13x9 baking dish with a non stick spray.
In a large mixing bowl, beat cake mix, water, oil and eggs together on high-speed until blended.
Pour cake batter into prepared baking dish and bake for 60 minutes or until tooth pick inserted comes out clean.
Remove from oven and after a few minutes, poke holes throughout the cake. Let cool
In a medium mixing bowl, beat cream cheese together until smooth and creamy, approximately 2-3 minutes.
In a small mixing bowl, beat banana pudding mix, vanilla and evaporated milk together until thick and creamy.
Add banana pudding to cream cheese and beat until well combined.
Once cake has cooled, add half the pudding mixture into a quart size freezer bag and clip the corner.
Squeeze banana filling into each hole then spread remaining pudding mixture over the top of the cake.
Spread cool whip over the top of pudding, cover with plastic wrap, place in fridge to chill.
Once chilled, sprinkle vanilla wafers over the top and add sliced bananas.