Begin by preheating your oven to 350 degrees.
Grease a cake pan or two brownie pans with non-stick spray.
Peel and mash the three ripe bananas with a fork and add them to a large mixing bowl with the yellow cake mix, banana creme pudding mix, cinnamon, nutmeg, and vanilla extract.
Slowly stir in the butter (make sure it is cooled or it will scramble the eggs).
Next add the eggs and water.
Blend well with a hand mixer for three minutes.
Pour into your baking pan.
Add the mini vanilla wafers and sliced bananas on top.
Bake at 350 degrees for 35 to 40 minutes or until a toothpick comes out clean from the center. You may need to cook slightly longer if using a rectangle cake pan.
Once cooled, top with whipped topping if desired.