Spread 1 slightly rounded teaspoon frosting on each cookie. For each scarecrow cookie, cut half cracker into shreds with sharp knife; place shreds on 2 sides of each frosted cookie to resemble hair.
Sprinkle work surface with sugar. Place 1 gumdrop on its side on sugar; flatten with rolling pin into 1/8-inch-thick triangle. Fold up one edge to form hat brim; place on cookie, trimming to fit if necessary.
Place 1 piece candy corn on cookie to resemble nose. Use black decorating gel to make eyes, mouth and hatband.