In a mixing bowl, beat the softened cream cheese until smooth and fluffy. Add the vanilla pudding mix and gradually pour in the cold eggnog while mixing until the mixture thickens.
Stir in vanilla extract, nutmeg, and cinnamon if using. Gently fold in the whipped topping until the filling is light and well combined.
Pour the mixture into the prepared graham cracker crust. Smooth the top with a spatula.
Cover and refrigerate for at least 4 hours, or overnight for best results. Before serving, top with additional whipped topping and a dusting of nutmeg.