Heat griddle or skillet over medium-high heat or to 375°F. Grease with vegetable oil or shortening (or spray with cooking spray before heating).
In medium bowl, stir pancake mix and water with fork or wire whisk until smooth (batter will be thin). Stir in banana and 2 tablespoons walnuts.
For each pancake, pour slightly less than 1/4 cup batter onto hot griddle. Cook until bubbles form on top and edges are dry. Turn and cook other sides until golden brown.
Top pancakes with sliced banana, 2 teaspoons walnuts and the caramel topping.