Using a medium-sized mixing bowl and a handheld mixer on medium-high speed, beat the cream cheese for 1 to 1½ minutes until smooth.
Sprinkle the instant pudding mix over the cream cheese and continue mixing for 1 more minute until well combined.
Add the marshmallow fluff and continue mixing just until incorporated.
Fold in the thawed Cool Whip.
Spread the Cool Whip mixture into the premade graham cracker crust. Chill in the refrigerator for 8 hours or overnight. Slice into 8 servings and garnish the outer edges of the slices with whipped topping if you wish.