Place peanut butter in a microwave-safe bowl; heat in microwave until smooth and creamy, 20 to 30 seconds. Stir graham cracker crumbs, sugar, and butter into peanut butter until evenly combined. Transfer to a 9x13-inch baking dish and press to form a crust. Refrigerate until chilled, about 2 hours.
Beat milk and pudding mix together in a bowl until thick and creamy; pour over crust. Top pie with whipped topping to serve.