Duke Ferris of Game Revolution noticed that the cover art for the same Kirby games shows a happy Kirby in Japan and an angry Kirby in America. There are four more examples at the link.
It's probably those full-body scanners that the TSA uses now that gets him angry.
http://www.gamerevolution.com/manifesto/happy-japanese-kirby-angry-american-kirby-500 via Digg