Preheat the oven to 425°. Line a 12 cup muffin pan with paper liners {or generously spray each cup with nonstick cooking spray} and set aside.
In a large bowl combine the pancake mix, brown sugar and cinnamon. Whisk {or sift} the ingredients together to remove any lumps.
Next, add the vanilla extract, eggs, melted butter, sour cream and mashed bananas to the dry mixture. Gently mix the wet ingredients into the dry ingredients and mix until just combined {be sure to not over mix}.
Use a large cookie scoop {or about 1/4 cup of batter} and fill each one of the muffin cups 3/4 full.
Bake for 5 minutes, then turn the oven down to 350° and continue baking for 15-20 minutes. You will be able to tell that the muffins are done by either pressing down on the muffin and it springs back, using a toothpick in the center and it comes out clean or until they are a light golden brown.
Cool in the pan for 10 minutes. Remove and serve. Leftovers can be stored in the refrigerator for up to 4 days in an airtight container.