Make cake in a 9x13 inch baking pan, according to the instructions on the back of the box. It will be easier to remove the cake later if you line the pan with parchment paper.
15.25 ounce box yellow cake mix, Ingredients needed to make cake
After baking and while cake is still warm, use a thick skewer or back of a wooden spoon to poke holes in the top of the cake.
Allow cake to cool completely.
Remove cake from the pan and place on a large serving platter.
In a medium bowl, add the 2 boxes of pudding mix and the milk. Whisk together quickly until combined.
Pour the pudding mixture over the cake quickly before it thickens in the bowl.
Place cake in the fridge for at least 30 minutes to set.
Spread cool whip over the top of the cake.
8 ounce container frozen whipped topping
Decorate with crush vanilla wafers and sliced bananas.
Notes
Cake mix: You could use a similar cake mix flavor, like white cake, if you prefer. I don't recommend going with a cake that has a lot of flavor, like a butter cake mix, as you'll lose some of the banana flavor in the cake.
Milk: I like to use whole milk for the richest pudding, but any type of milk, including nondairy milk, should be fine.
Frozen whipped topping: You can use Cool Whip, TruWhip, or a similar type of frozen whipped topping in this recipe.