MIX crushed pretzels, sugar and butter. Press firmly onto bottom and up side of 9-inch pie plate. Refrigerate until ready to fill.
COMBINE condensed milk, lime juice and drink mix in large bowl until well blended. Gently stir in whipped topping. Pour into crust.
FREEZE 6 hours or overnight. Let stand at room temperature 15 min. or until pie can be cut easily. Store leftover pie in freezer.