The intergalactic chickens assaulted the solar system and tried make sure that every planet was inhabited exclusively by chickens. It was only you who managed to repel the invasion, and saved humanity from an eternity of servitude. They came out of nowhere, and everywhere. Intergalactic chickens invaded Earth, seeking revenge for the oppression of their earthly brethren. We should have known the time would come for us to pay. And it did. For centuries we have oppressed them, grilling, roasting, stewing, and stuffing them in buns.