Beat eggs in a bowl and add milk, oil. Then stir in sugar and pumpkin puree until smooth. Mash banana with a fork and add into wet ingredient mixture.
In another bowl mix together flour, baking powder, and salt. Slowly incorporate dry mixture into wet until combined well.
Mix together melted butter, chopped pecans, brown sugar and flour listed to make topping. Set aside.
Line muffin pan with liners and fill 3/4 of the way full with batter. Sprinkle topping on all or some of them, gently pat down with fingers just so it sticks.
Bake for 18-20 minutes until toothpick comes out mostly clean with some crumbs on it when inserted into center. You want some crumbs meaning they are still moist, I do not like overbaked and dried out muffins so I am kinda' specific about this part.
Remove from oven and pan. Allow to cool some while you prepare icing if desired. In a bowl melt butter and mix with powdered sugar, vanilla and enough hot water to thin it out to desired consistency.