Mix crushed pretzels, sugar and butter. Press firmly onto bottom and up side of 9-inch pie plate. Refrigerate until ready to fill.

Compine condensed milk, lime juice and drink mix in large bowl until well blended. Remove 1/2 cup whipped topping; set aside. Gently stir in remaining 2-1/2 cups whipped topping. Pour into crust.

Freeze 6 hours or overnight. Let stand at room temperature 15 min. or until pie can be cut easily. Garnish with reserved whipped topping before serving. Store leftover pie in freezer.