1Heat oven to 350°F (325°F for dark or nonstick pans). Grease or spray two 8- or 9-inch round cake pans. In large bowl, beat cake mix, water, oil and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Divide batter between pans. Bake and cool cake as directed on box for 8- or 9-inch rounds. For easier handling, freeze cooled cake 45 minutes or until firm.
2Cut 1 cake in half lengthwise, making 2 half-circles. Sculpt 1 half-circle into a head and the other half-circle into a tail. For body, cut 1-inch slice from edge of remaining whole cake. From cut edge, cut out a small inverted U-shaped piece. Place body on tray; arrange head and tail pieces next to body.
3Spoon frosting into large bowl. Stir in enough food color until desired green color. Attach cake pieces with a small amount of frosting. Frost cake with a thin layer of frosting to seal in crumbs. Refrigerate or freeze cake 30 to 60 minutes to set frosting. Frost entire cake.
4Decorate with yellow candies. Add chocolate chips for eyes. Store loosely covered.