Add the canned pumpkin, ripe banana, Greek yogurt, and chilled almond milk to your blender. Pulled together, these form the creamy base of the smoothie.
Sprinkle in the ground cinnamon, ground nutmeg, and pour in the vanilla extract. For a touch of sweetness, add honey or maple syrup if desired.
Secure the lid and blend on high for about 30-60 seconds, until the mixture is completely smooth and velvety. You should see a bright orange, frothy liquid with no visible chunks.
Stop the blender and remove the lid. Give the smoothie a quick check—if it's too thick, feel free to add a splash more almond milk and blend briefly to loosen it.
Pour the smoothie into glasses, and if you like, garnish with a tiny sprinkle of cinnamon or a dollop of whipped cream for presentation.
Enjoy immediately for the best chilled texture, or refrigerate for up to an hour to enhance the coldness before serving.