Mix pumpkin puree, instant pudding and pumpkin pie spice.
Gently fold in Cool Whip and pour into graham cracker crust.
Chill at least 2 hours and serve.
Notes
How you want to use the fluff determines whether to use 8 ounces or 16 ounces of cool whip. The cool whip adds a lighter, creamier flavor to the pumpkin. So in a dip I like the stronger pumpkin flavor. In a pie I like the lighter cream pie flavors. You can always start with 8 ounces, sample it and stir in more cool whip as desired.
I have better luck folding this together by hand than using a mixer