Preheat the oven to 350°F. Combine the graham cracker crumbs, melted butter, brown sugar, and cinnamon. Press firmly into the bottom and sides of a 9-inch pie plate.
Bake for 8–10 minutes, then cool completely. You can also refrigerate the crust instead of baking it, although baking helps it hold together when sliced.
In a medium bowl, whisk the pumpkin spice pudding mix with 1 cup cold whole milk for 2 minutes. Refrigerate for 5 minutes until thickened.
In a large mixing bowl, beat the softened cream cheese, powdered sugar, and vanilla until smooth.
Add the prepared pumpkin spice pudding to the cream cheese mixture and beat until fully combined.
In a separate bowl, whip 1 cup cold heavy cream until stiff peaks form.
Gently fold the whipped cream into the pumpkin cheesecake mixture until smooth and fluffy.
Fold in the 4 chopped oatmeal creme pies. Keep the pieces fairly large so you get little pockets of cookie and creme filling throughout the pie.
Spread the filling into the cooled graham cracker crust, smoothing the top.
Refrigerate for at least 6 hours, preferably overnight, until firm.
For the topping, whip the remaining heavy cream, powdered sugar, and vanilla until stiff peaks form.
Pipe a swirl of whipped cream on each slice of pie. Finish with a little cinnamon sugar.