With all the excitement of Grandpa Yook's story, you might have forgotten that it's actually Young Yook who's giving us all the goods.
Like his grandpa, this guy doesn't get a name. And all we really know about him is that he's kind of a rebel. After all, when Grandpa finds him, he shouts, "You should be down in that hole! / And you're up here instead!" (184-85). Was Young Yook trying to make a point?
This little guy is still young enough that maybe—just maybe—he's not fully assimilated into the Yook-Zook conflict. Why does that matter to us? Because it allows us to picture ourselves in his place and think about things for ourselves. He's kind of a doorway into the book. As readers, we are pulled into the character of the young Yook, left to respond on our own to the scary and desperate situation at the end.
And because we know that The Butter Battle Book is an allegory (check out "Symbolism, Imagery, and Allegory" for more), we're able to bring the book back out into our world, too. So how do we butter our bread?