Preheat your oven to 350°F. Cream peanut butter and butter with an electric mixer until light and fluffy.
Add brown sugar.
Add eggs and vanilla and beat until well mixed.
Add banana, baking soda, and salt.
Mix in all purpose flour, whole wheat flour, and wheat germ. Mix until just combined.
Stir in oats and your optional mix-ins like chocolate chips, peanut butter chips, and walnuts.
Drop onto a baking sheet, about 4 inches apart. Bake in the oven for 15 minutes until the cookies are set and lightly browned. Cool for 1 minute on sheet and cool completely on a wire rack.