In a medium bowl, combine cereal, flour, sugar and baking powder; set aside.
In a small bowl, combine milk, egg, melted butter and mashed banana. Stir wet ingredients into dry ingredients until just blended. (Batter will be slightly lumpy). Let stand 10 minutes then stir in walnuts.
Heat a lightly greased griddle or skillet over medium-high heat. Pour scant 1/3-cup batter onto the griddle or skillet for each pancake. Cook until bubbles form on the top, about 3 – 5 minutes, then flip and cook until done, about another 5 minutes. Serve immediately, topped with sliced bananas and syrup, if desired.