Heat skillet or griddle over medium-high heat or to 375degreesF. Grease with vegetable oil or shortening. In medium bowl, stir pancake mix and water with fork or wire whisk until smooth (batter will be thin). Stir in mashed banana and 2 tablespoons walnuts. For each pancake, pour slightly less than 1/4 cup batter into hot greased skillet. Cook until bubbles break on surface and edges just begin to dry. Turn; cook about 1 minute or until bottoms are golden brown. Serve pancakes topped with sliced banana, 2 teaspoons walnuts and the caramel topping.