Mix pretzel crumbs, sugar and butter; press onto bottom and up side of 9-inch pie plate. Refrigerate until ready to fill.
Mix next 3 ingredients in large bowl. Whisk in 2-1/2 cups Cool Whip. Pour into crust.
Freeze 6 hours. Remove from freezer 15 min. before serving; let stand at room temperature until slightly softened. Garnish with remaining Cool Whip.
Notes
MAKE IT EASY For easy serving, dip pie plate into warm water, just to rim, for 30 seconds. SPECIAL EXTRA For stronger lime flavour, stir in 2 Tbsp. lime zest with the lime juice.