Combine milk with pudding mix in a bowl. Beat with an electric mixer or a whisk for 2 minutes, or until thoroughly blended. Set aside.
In a 9-inch square baking pan, arrange a layer of wafers, flat sides down, and then top with a layer of banana slices. Continue alternating layers until all of the wafers and banana slices are in the dish.
Top the dish with the pudding and let it seep down in between the wafer and banana layers. Cover and refrigerate for 2 to 3 hours. If desired, add whipped topping before serving.
PER SERVING (1/6th of recipe, about 1/2 cup): 137 calories, 1.5g fat, 299mg sodium, 29g carbs, 1g fiber, 15g sugars, 4g protein