Combine flour, baking powder, brown sugar and salt in a large bowl. Mix in the peanut butter until the texture resembles cornmeal. Add milk and vanilla; stir just until blended. Stir in the banana pieces.
Heat a large skillet over medium heat and coat with cooking spray. Spoon batter onto the skillet, using approximately 2 tablespoons to form each pikelet. Cook until pikelets are golden brown on both sides; serve hot.