Preheat oven to 400°F. Combine oats, flour, flaxseeds, cinnamon, baking powder, baking soda, nutmeg, and salt. In another bowl mash the banana and mix with the oil and vanilla extract. Slowly combine wet mixture into dry mixture. Fold in carrots and pineapple until combined.
Spray a 12-cup muffin pan with nonstick cooking spray or use cupcake liners. Pour batter evenly into each cup. Bake 15 to 20 minutes until golden and a toothpick inserted in the center comes out clean.