Sonic Adventure
Sonic Team's Takashi Iizuka stated in an interview with video game publication 1UP.com that Chao were incorporated into "Sonic Adventure" "so that new players would be forced to go out, explore the action sections, and find Flickies and things." Chao were designed as a "relative neutral entity" in this game. However, to remain consistent with the good–evil dichotomy of "Sonic Adventure 2", they were designed so that the player could raise them as "Hero Chao" or "Dark Chao". Chao were given the ability to socialize and interact in "Sonic Adventure 2" in order to make the game unique, and to more resemble "a real artificial life form."