Trace an existing dome-shaped fleece hat onto a double layer of polar fleece. Trace around your outline again, one inch out from the original line.
Draw two cat ear shapes onto a double layer of fleece and then draw around your outline again, one inch out from your original line. Cut the pieces out along the second line.
Pin the ears along the original tailor's chalk line and then sew them along three sides with matching thread on your sewing machine. Turn them inside out so that the seams are hidden. Cut the pieces out along the second line.
Place your sewn ears between the two layers of cut polar fleece that will form your hat. They should be positioned at the top of the hat and so that the remaining raw edge meets the raw edge of the other two layers of polar fleece.
Pin your hat along the original tailor's chalk line and then sew along that line using matching thread on your sewing machine. Trim away excess polar fleece and turn the hat inside out. The cat ears will now be exposed at the top of your completed anime hat.