In a medium bowl, combine graham cracker crumbs, granulated sugar, and melted butter. Stir until fully mixed and the crumbs are moistened. Pack the mixture firmly into the bottoms of your serving cups using the back of a spoon or your fingers, creating a smooth base. Set aside.

In a large mixing bowl, beat the cream cheese with an electric mixer on medium speed until creamy and smooth, about 2 minutes. Gradually add the powdered sugar, mixing well until fully combined. Then, blend in the key lime juice and lime zest for 1-2 minutes until the filling is light and fluffy.

Gently fold in the whipped topping into the cream cheese mixture until just combined, ensuring the airy texture of the filling is maintained.

Spoon the key lime filling evenly over the prepared graham cracker crusts in each cup, smoothing the tops gently with a spatula.

Cover the filled cups with plastic wrap or a lid and place them in the refrigerator. Chill for at least 2 hours, or until set.

When ready to serve, remove the cups from the refrigerator, garnish with additional whipped topping and lime zest or a slice of lime, and enjoy.