So what's the deal with this Wall dividing Yook from Zook? Why does Grandpa seem so bummed out?
We learn that the Wall was built to keep the Zooks out. But it could've also been built to keep the Yooks in—we're not sure.
One thing's clear, though: there's no love between Yook and Zook because, as Grandpa tells the young Yook, "In every Zook house and in every Zook town / every Zook eats his bread / with the butter side down" (16-18).
Yooks, on the other hand, eat their bread "with the butter side up" (22).
Seems silly, right? Why can't they get along even though they eat their bread differently?
The drawing of the Zooks doesn't look too frightening. As a matter of fact, they look very much like the Yooks, just with different colored clothes.
The problem is that little differences like this very quickly translate to value judgments.
Grandpa says the Yook way of buttering bread is "the right, honest way!" (23). But the Zooks' way of buttering bread is a "terribly horrible thing" (15).
Of course, judging actions is a slippery slope to making dangerous generalizations as Grandpa does when he explains, "Every Zook must be watched! / He has kinks in his soul!" (26-27)
So Grandpa does what he thinks must be done and joins the "Zook-Watching Border Patrol" (29). Sounds like trouble.