Prepare cake mix according to package directions. Pour batter into a greased and floured 13" x 9" baking pan; set aside. In a large bowl, mix together ricotta cheese, eggs, sugar and vanilla. Carefully pour mixture over cake batter; do not stir. Bake at 350 degrees for one hour and 10 minutes. Cool cake completely in pan. In a bowl, whisk together milk and dry pudding mix; fold in whipped topping. Spread over cooled cake. For Snake Decoration, color 1 cup whipped topping with green food coloring. Pipe on top of cake in snake shape. Color 3 tablespoons of whipped topping with yellow food coloring. Pipe two dots for eyes. Add fruit leather tongue. Sprinkle with colored sugars. Refrigerate until ready to serve.