Place the softened cream cheese in a large bowl. Beat on high with a hand mixer until light and fluffy. Add the peanut butter and beat until combined.
Add the powdered sugar and milk, and beat until combined.
Fold in the whipped topping. Pour into the graham cracker crust. Refrigerate until firm, at least 4 hours or up to 24 hours.
Top with chopped peanuts and serve.
Notes
The best type of peanut butter for this pie is a regular variety (not drippy). It can be either smooth or crunchy, depending on your preference. I used creamy Skippy Natural. Regular Skippy or JIF work great, too. Any leftover pie should be stored in the refrigerator. It'll keep for several days in a covered container. You can also freeze the pie for up to 3 months. It's very good eaten while frozen, too! Wipe the knife on a paper towel in between slices to get clean looking slices. Variations:
Replace the whipped topping with 1½ cups heavy cream, whipped until stiff peaks form (measure 1½ cups first, then whip)
Try chunky peanut butter instead of smooth
Use an Oreo crust, a pretzel crust, or a traditional pastry crust (this Crisco pie crust is so flaky and tender)