Prepare pie filling mix with 2 1/4c milk as directed on package for pie. Measure 1 cup filling; set aside. Pour a thin layer of the remaining filling into pie shell. Set aside half of 1 banana. Slice 1 1/2 bananas and arrange slices on filling in shell. Top with remaining filling. Fold whipped topping into measured filling; spead carefully over filling in shell. Chill 3 hours. Garnish with additional whipped topping and reserved banana sliced.