Set aside and refrigerate 1/2 cup Cool Whip for garnish. In a large bowl, whisk the Dr Pepper, milk and pudding mix for 2 minutes. Fold in half of the remaining Cool Whip. Spread into GF graham cracker crust.
Spread remaining Cool Whip over pie. Refrigerate for at least 8 hours or overnight.
Dollop reserved whipped topping over each serving;