Prepare the pudding: In a large bowl, whisk together the instant pudding mix and cold milk until smooth. Let the mixture sit for about 5 minutes to thicken.
Prep the bananas: In a small bowl, combine the sliced bananas with lemon juice to prevent browning.
Combine ingredients: Gently fold the whipped topping into the thickened pudding. Stir in the prepared bananas, marshmallows, and vanilla wafers until evenly distributed.
Serve: Serve immediately or refrigerate for a few hours. The vanilla wafers will soften slightly in the refrigerator.
