If you've already played TNI, you probably met at least one chicken.
And if you met that chicken, you're probably wondering where it comes from.
So the next question is: have you played Zelda: Ocarina of Time, before?
If you have, you probably know there are some wicked chickens that become warrior-chickens when attacked. Well, not REALLY warriors, but they know how to fight back if you bother them.
A game designer on TNI got traumatized by these non standard chickens, and wanted to get his revenge. One of the solutions was to put them in TNI as ennemies, so the players could fight them AND DESTROY THEM ALL.
That's how these birds ended in TNI.
But we're not monsters; we gave them shiny armors and dignity, so they fight with honor.