Anytime before Thanksgiving, spoon the pumpkin pie filling into muffin cups, then cover the pan with aluminum foil and place it in the freezer.
When you're ready to make the smoothies, add the milk to a blender. Then add the yogurt. Pop 4 pieces of the frozen pumpkin pie filling out of the pan and add to the blender. (Save the rest of the pie filling for another time, or for a second batch of smoothies if one isn't enough to calm the hungry beasts.)
Next, add the cinnamon. Then blend the mixture until totally smooth and pour it into individual glasses.
Sprinkle the tops with graham cracker crumbs before serving.