1. Preheat the oven to 350°F. Grease and line two 8-inch round cake pans.

2. In a large bowl, mix the yellow cake mix, eggs, vegetable oil, and water until smooth.

3. Divide the batter evenly between the prepared pans and bake for 24 to 28 minutes, or until a toothpick inserted in the center comes out clean.

4. Let the cakes cool in the pans for 10 minutes, then transfer them to wire racks and cool completely.

5. In a mixing bowl, whisk together the instant vanilla pudding mix and cold milk until smooth and thickened. Chill for 5 minutes.

6. In another bowl, beat the heavy whipping cream with powdered sugar and vanilla extract until fluffy peaks form.

7. Place one cooled cake layer on a serving plate. Spread a layer of vanilla pudding over the top, then add a layer of sliced bananas.

8. Set the second cake layer on top and spread the remaining pudding over it.

9. Spread or pipe the whipped topping over the cake.

10. Sprinkle the crushed vanilla wafers over the top.

11. Chill the cake for at least 2 hours before slicing and serving.