Prepare the Cake:
Prepare the cake mix according to the package directions for a 9×13 cake.
Cool and Poke Holes:
Once the cake comes out of the oven, let it cool for a couple of minutes. Using a wooden spoon handle, spatula handle, or similar-sized object, poke big holes all over the cake, reaching down to the bottom.
Make the Pudding:
In a bowl, whisk together the instant banana pudding mix with 4 cups of milk until smooth and lump-free.
Pour Pudding Over Cake:
Pour the pudding mixture over the cake, focusing on filling the holes. Use the back of a spoon to gently push pudding down into the holes.
Chill:
Put the cake in the refrigerator to set and cool for about 2 hours.
Add Whipped Topping:
After the cake has completely cooled, spread the thawed whipped topping evenly over the cake.
Prepare Vanilla Wafers:
Crush the vanilla wafers by placing them in a ziplock bag and gently crushing with a rolling pin. Leave some pieces larger for crunch.
Add Wafers:
Sprinkle the crushed vanilla wafers on top of the whipped topping. For maximum crunch, add the wafers just before serving.
