For hair, tint shredded coconut with red and yellow liquid food coloring.
Cut the cheesecake into 1-inch-wide wedges. trim the short curved edge of the wedge to straighten it. Make a straight cut into the edge of the cookie (hat brim). Place the cookies against the cheesecake wedge to check the shape; trim the cookie brim as needed.
Dip the cheesecake into melted semisweet chocolate chips. Before the chocolate sets, sprinkle with nonpareils and set cookie brim in place.
Before serving, place the hat on a plate. Using a small scoop, form a ball of lime sherbet for the head. Place the head against the brim and decorate with candies for eyes, sprinkles for brows and a mouth, and half a cashew for the nose. Press coconut in place for hair. Return to the freezer until serving time.