Combine bran cereal, bananas and yogurt in a medium bowl. Let stand for a couple minutes to allow cereal to soften. Meanwhile, combine flour, baking powder, baking soda, salt, and nuts and/or raisins in a large bowl; set aside.
Stir eggs, sugar and oil into bran mixture, then add to dry ingredients; stir just until combined.
Spoon batter evenly into 12 greased or paper-lined muffin cups.
Bake in a preheated 400 degrees F (200 degrees C) until tops spring back when pressed, about 17 to 20 minutes. Let muffins cool in pan for a few minutes, then remove to a wire rack to finish cooling. Store in an airtight container.
