There's nothing like baking when it's 93 degrees, but I had loads of time and four brown bananas calling my name. I substituted crisco for butter and added what butter I had for flavor. You can't taste the difference, although the texture is less moist. Walnuts add the perfect crunch and I spiced with a touch of nutmeg and cinnamon, not immediately recognizable but I think they add a little "home" to the muffins. Also, adding some roughly mashed bananas with the nuts (after mixing dry into wet) is a great tip I learned from an online recipe. The chunks mean pockets of sweet cooked banana in the mix, as opposed to just flavored batter. Only thing I'd change: add some honey. These aren't quite as sweet as I like.
It was a sweaty endeavor having the oven on to bake them, but I lay in the luxury of our new AC afterward as a reward.