Set aside and refrigerate 1/2 cup whipped topping for garnish. In a large bowl, whisk the root beer, milk and pudding mix for 2 minutes. Fold in half of the remaining whipped topping. Spread into graham cracker crust.
Spread remaining whipped topping over pie. Refrigerate for at least 8 hours or overnight.
Dollop reserved whipped topping over each serving; top with a maraschino cherry if desired.
Originally published as Root Beer Float Pie in Healthy Cooking June/July 2012, p56