Banana Strawberry Cupcakes/Muffins?

OK. I had some left-over overripe bananas and some fresh-from-the-market -strawberries, and thought I'd make the strawberry banana cupcakes from Vanilla Garlic. Followedthe recipe exactly, except I substituted 6TBSP olive oil for 6 TBSP of the vegetable oil. They came out more like muffins than cupcakes. (Cupcakes=light and spongy, muffins=thick and dense. ) But I frosted them anyway as the recipe suggested. Good, but not great.