The Chief Yookeroo is the top dog, the commander-in-chief, the big cheese. And boy does he milk it. This guy gets to benefit from the Yook-Zook conflict while avoiding its consequences.
The main thing we know about him is that he's always chipper. Seriously, even as the drawings of his office become messier, he remains majorly confident in Yook dominance. Early on in the arms race, Chief Yookeroo appears all smiles as he says to Grandpa, "'You're not to blame. / and those Zooks will be sorry they started this game" (46-47). At this point, the conflict really is just a game to the guy. He doesn't want to get his Chief clothes dirty, after all.
Gradually, the conflict—or at least a shadow of it—finds its way to the Chief's office. In his final appearance, he seems confident: "'Everything is all right. / My Bright Back Room Boys have been brighter than bright" (163-64). But wait a second. That glass-half-full attitude is pretty sharply contrasted illustration, in which the chief is peeking out of the "Top-est Secret-est Brain Nest." A picture is worth a thousand words, and it's pretty clear this guy's worried.
Why can't the chief express his doubt in the Yooks? Why is he stuck with this "Yooks are the bestest" mentality even if it might mean his demise?
Seriously, we're asking.