- Preheat oven to 350º and grease and flour a 9-x-13″ cake pan. Prepare yellow cake mix according to box instructions. Pour batter into prepared pan and bake until a toothpick inserted in the center comes out clean, about 25 minutes. Let cool 10 minutes.
- Meanwhile, prepare pudding: In a small bowl, whisk together pudding packets and milk until thick. Set aside.
- In another large bowl, beat cream, sugar, and vanilla until stiff peaks form. Set aside.
- Using the bottom of a wooden spoon, poke holes all over the cake. Spread pudding mixture on top and top with a layer of banana slices. Spread whipped cream on top and sprinkle all over with crushed and whole Nilla Wafers and bananas.
- Slice and serve.