This costume might be one of the easiest ones on this list to make, but that doesn't mean it lacks quality. It only requires a few materials.
What you'll need for this Poliwhirl costume:
Cut out a circle from the white felt. How much will depend on the size of the sweatshirt you use, but you want it to cover most of the torso. Draw a spiral with your pen, then glue the circle to the shirt. For the eyes, cut out two large ovals from the white felt. Shade in the black portion with your pen, then glue the eyes to the hood.