"Why is the Angry Bird, Angry?"

Because marketing determined that anger refers to a low-level system in the human body; its use is thereby likely to trigger greater emotional stimuli than say, the use of boredom, or jest. Appropriate emotional stimuli results in higher rates of memory imprinting, generically referred to as 'stickiness.' In short, it would help to sell more apps.

Of course, it was a three-year-old who asked this question, and her father who posted it on the web.