In a medium bowl, mix together the graham cracker crumbs, sugar and melted butter. Press into the bottom of a pie plate, pressing up the sides as well.
In a large bowl, whisk together the sweetened condensed milk and key lime juice until a smooth consistency has formed. Fold in the whipped topping.
Cover and refrigerate for at least 4 hours or overnight until the filling is fully set.
Right before serving, cut thin slices of lime, then cut into quarters - you’ll need 12 quarters. Zest another lime.
Add about 1 cup of whipped topping to a piping bag equipped with a star tip, and pipe out one star on the edge, then another directly across from it, then one halfway between those, and another on the opposite edge. Now pipe two stars in between each of those. You should have 12 stars.
Add a quarter lime slice onto the center of each star. Dust the pie with lime zest for an added pop of color.To serve, cut into 6 regular, or 12 small slices.