In a large bowl, whisk milk and pudding mixes for 2 minutes. Fold in whipped topping.
In a 13-in. x 9-in. dish, layer a third of the graham crackers and half of the pudding mixture. Repeat layers. Top with remaining graham crackers. Refrigerate for at least 1 hour.
Spoon frosting into a microwave-safe bowl. Cover and microwave on high for 15-20 seconds or until softened, stirring once. Spread over graham crackers. Cover and refrigerate for at least 20 minutes or until frosting is set. Yield: 15-20 servings.