The night before you intend to eat the parfait, combine the oats, yogurt, milk, pumpkin, spices, and vanilla extract in a bowl. Cover with plastic wrap and refrigerate overnight.
Also the night before, place the banana slices in a ziploc bag and freeze overnight.
In the morning, place the frozen banana slices into a food processor (or high-speed blender) and process/blend until smooth and creamy.
Place the graham crackers into a plastic bag and crush with a skillet or other heavy item until they turn into coarse crumbs.
Layer the cold pumpkin spice oats with the banana soft serve and graham cracker crumbs.