You can use a banana to substitute for an egg in a recipe.
My husband and I were trying to eat everything we had from the cabinets and refrigerator last month. I wanted to make something sweet, but didnt have any eggs. I tried this recipe from a fellow blogger, Rachel. And guess what?!? It worked! The muffins turned out GREAT!
I am watching my cholesterol, so anytime I can substitute a banana with an egg, I will. I also used applesauce in place of the oil in this recipe.