Ah, this is a hard one.
I'll admit, the first thing that came to mind was macaroni and cheese. And not the homemade kind, either. The Kraft boxed kind that I grew up on.
I've always been slightly obsessed with that yellow stuff. Did you know that it originally sold for just 19 cents?  During World World II, Kraft sold 50 million boxes of their product.
However, I think I'll be a little healthier than that. I found a strawberry banana smoothie recipe online that my kids and I love. It has bananas and strawberries (obviously), yogurt, and orange juice. I'm not sure if that is cheating, though, because it's technically four foods rolled into one?
The recipe can be found here: http://www.rachaelray.com/2014/05/super-simple-kid-friendly-smoothies (we omit the honey).