In a medium mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter. Press mixture into the bottom of individual serving cups, creating a compact layer.

In a large mixing bowl, beat softened cream cheese with an electric mixer on medium speed until smooth. Gradually incorporate powdered sugar, then slowly add key lime juice and optional lime zest. Blend until light and fluffy.

Gently fold in whipped topping using a spatula until fully blended with the cream cheese mixture.

Spoon the creamy filling into each prepared crust, smoothing the tops. Cover with plastic wrap or lids.

Refrigerate for at least 2 hours, or until set. Letting them sit overnight enhances flavors.

Before serving, optionally top each cup with extra whipped topping and a sprinkle of lime zest, along with fresh fruit or lime slices.