To make a lime margarita Kool-Aid pie, line a pie plate with a crumb crust, make the filling, add whipped topping, fill the crust, and freeze the pie for six hours. Thaw the pie, and top with additional whipped topping before serving.
To make the pie's crust, melt 6 tablespoons of butter. Combine 1 1/4 cups crushed salted pretzels, 1/4 cup white sugar and the melted butter. Press the crumb crust mixture into a 9-inch pie pan, covering the bottom and the sides. Refrigerate the crust while you prepare the filling.
Empty 1 envelope lemon-lime Kool-Aid mix into a mixing bowl, and add 1/2 cup of lime juice and 14 ounces of sweetened condensed milk. Stir thoroughly until the Kool-Aid dissolves, and fold in 2 1/2 cups whipped topping. Stir the filling until it is smooth and creamy.
Remove the chilled pie crust from the refrigerator, and spoon the filling into it. Freeze the pie uncovered for at least six hours. About 15 minutes before serving time, take the pie out of the freezer, and let it thaw at room temperature. Smooth whipped topping over the surface, and slice the pie. Serve the pie immediately. Refrigerate or freeze the leftovers.