I like to use Peanut Butter instead of butter and then if you want to be really bad, ice them with chocolate ganache.
Peanut butter with Cocoa Krispies has been one of my variations. I’ve tried to work in some banana, but it didn’t turn out quite right ... I was mashing it and adding it to the peanut butter, I think next time, I’ll just chunk it up small and stir it in like choccy chips.