The word Chao is a pun on Chaos, a word commonly used in the Sonic series.Ĭhao made their first appearance in Sonic Adventure for the Sega Dreamcast, later in Sonic Adventure 2, and further enhanced in Sonic Adventure 2: Battle and Sonic Advance. Chao are somewhat complex, responding to stimuli they have moods, they require food, and they can be loving or fearful. Their role in the games is to be raised by the player in mini-games, similar to Tamagotchi. A Chao is an artificially intelligent, virtually generated lifeform from the Sonic the Hedgehog series.