Chao (pronounced /ˈtʃaʊ/, plural form also Chao) are relatively small, sentient creatures found in numerous Sonic the Hedgehog media, especially the video games. They serve as a way to introduce both artificial life (in the programming, not in the franchise's universe) as well as more plot to the franchise. They are based on earlier forms of the technology behind them, known as A-life, which appear in NiGHTS into Dreams with the Nightopians. Chao appear in the following Sonic games:
Chao begin life in an egg, similar to many animals in the real world (particularly non-mammals). When they hatch, they can be trained in many different ways, having multiple different attributes and emotional states. The chao from Sonic Adventure 2 can also favor "dark" and "hero" sides which can lead to variations in visual evolution. Depending on the game, they take various times to evolve. When evolving they go back into their cocoon state (similar to their normal egg state) for a small amount of time. In Sonic Adventure 2, it will take about 8-20 hours spent in a Chao Garden before they either die or reincarnate (depending on how you treat them). They can only reincarnate two times, even if treated well before dying. When they die for the final time, they go into a white cocoon. Chao can also be trained to "ultimate forms" such as the Chaos Chao, the Devil Chao and the Angel Chao. The three variations are all immortal, but do not have the ability to mate and make more chao.'
Chao can be trained with Chaos Drives from GUN robot enemies in Action Stages or animals either found out in the open or in various badniks made by Dr. Eggman. Red represents power, Green represents speed, Yellow represents swimming and Purple represents flying. (Getting the drives could also be done by trading them for rings in Sonic Adventure 2: Battle.) Animals can also affect their appearance; for instance, rabbits can give chao rabbit ears. Various fruits can be bought either in-game (like in Sonic Adventure 2: Battle), in Chao Adventure, or in the Tiny Chao Garden that serve a similar purpose. Plus, in the first Sonic Adventure, feeding the nuts found on the trees gives chao different stats, but it depends on who you play as (for instance, Sonic raises their speed, Tails raises their flight, Big raises their swim... the only one who has no effect is Gamma).
Chao are based on a special technology called A-Life, which originally came from NiGHTS into Dreams on the Sega Saturn where it was used for the Nightopians. They looked like small elves (peach colored) with bald heads and little blue clothes. However, despite their lower IQ to chao, the Nightopians did have emotions which were reflected in the music they sang and the music in the stages. They could die and become cross-bred with stage enemies (creating things called Mepians), and were born from small white eggs similar to those of the birds.
Possibly the most famous Chao is Cheese the Chao, the invincible partner of Cream the Rabbit (the walking, talking and flying rabbit) which can be seen in action in Sonic games (Namely Sonic Advance 2 and Sonic Heroes) as well as being a character in Sonic X, a Sonic anime that is now airing in America and a cameo in GameCube's Sonic Adventure DX, a remake of Sonic Adventure for the Dreamcast.
As with the Chao of earlier Sonic manga and magazines, Cheese retorts "Chao Chao Chao" instead of talking. This is said to be taking advantage of the Pokémon craze, but this is not true as many fictional Japanese animals said their name rather then talking long before Pokémon. However, this speech aspect is not true to all Chao, as Chao from the games often purred or make simple noises rather then simply saying their name.
Chao come in many forms, and the way they are raised has a large impact on their physical appearance and emotional growth. There are however a few 'basic' forms of chao that can be achieved through selective breeding. These too are divided into two groups: alignment and attributes.
Chao begin life in a neutral alignment. During their first stage of life, their later development is determined on how they are treated. They can, after they evolve, become either a Hero Chao or a Dark Chao. In Sonic Adventure DX, alignment is altered based on special foods given to the chao. In Sonic Adventure 2, being good to the chao, such as picking them up, rocking them, and petting them, will make the chao favor the alignment of the character that is doing the action. Sonic, Tails, and Knuckles are the Hero characters in the game, while Shadow, Rouge, and Dr. Eggman are the Dark characters. Harming the chao, via throwing them, stepping on them, or actively attacking them, makes them favor the opposite alignment of the character.
In Sonic Chronicles: The Dark Brotherhood, Chao eggs can be found scattered throughout the game, from Green Hill Zone to the Nocturne fortress. Chao hatch from these eggs over time, and are deposited in the "Chao Garden" (which is not an actual accessible location as in the Sonic Adventure games, but can be viewed from the game menu).
The various Chao which hatch have profound usefulness in the game's combat system. Equipping a fighting character with a chao confers a variety of different combat advantages.
There are 45 different chao in all, five of which (the "viral" chao) could not be accessed with through conventional play. These five "viral" chao were supposed to be unlocked at special Sega events - which were later apparently canceled. Multiple copies of each of the 45 chao can be collected. (Note: The descriptions for the viral chao were presumably not giving to beta testers and as a result not checked over. Though they work, 3 of them have descriptions that are longer than the game can display. The full descriptions found in the ROM image are listed for those.)
|Baki||Viral*||Ninja-style black with a black head-orb and pink face||Bonded character making a successful counter move will automatically get free attacks against the enemy.|
|Barbo||Common||Dark blue with red/white extremities and a green head-orb||Increases Maximum HP of bonded character.|
|Belgog||Rare||Blue with light blue extremities and a pink head-orb||Bonded character is much harder to hit.|
|Bepke||Rare||Black/white with white horns and a red head-orb||One enemy will automatically attack the bonded character instead of other team members.|
|Blayze||Rare||Light grey with brown extremities and a red head-orb||Bonded character does much more damage in battle.|
|Bobo||Rare||Black/magenta with magenta horns and a yellow head-orb||Bonded character will always find an extra reward item after combat.|
|Cheese||Unique**||Cream's best friend in the whole wide world: Light blue with a red bow and yellow head-orb||Greatly increases the luck of all team members.|
|Cheezlet||Common||Light blue with white extremities and a yellow head-orb||Bonded character does more damage in battle.|
|Choo||Common||White with magenta extremities and a pink head-orb||Bonded character regenerates PP at the start of each combat round.|
|Choopaloo||Unique||Orange with horn-like ears, purple extremities, and a light blue head-orb||Increases XP gained from each battle.|
|Churdle||Common||Aquamarine with light blue extremities and a pink head-orb||Bonded character has a better chance of hitting targets in battle.|
|Dusty||Rare||Purple/yellow with blue extremities and a blue head-orb||Increases the chance that the team will catch a fleeing opponent.|
|Farfinkle||Viral*||Ninja-style black with a black head-orb and orange face||Bonded character automatically inflicts a random status effect on enemy when making a normal attack.|
|Ferox||Unique||Green with a grey muzzle, aquamarine extremities, and a red head-orb||Bonded character automaticly succeeds using their POW moves.|
|Fess||Rare||Black/blue with blue horns and a light blue head-orb||Increases the odds that Chao eggs will hatch rare or unique Chao.|
|Fimbley||Viral*||Ninja-style black with a black head-orb and blue face||Bonded character will automatically be missed some basic attacks each round.|
|Ghise||Common||Dark blue with pale blue extremities and a light blue head-orb||Bonded character's attacks do Water damage.|
|Gibber||Rare||Purple with blue extremities and a pale blue head-orb||Bonded character has greatly increased resistance to damage.|
|Griff||Common||Pale blue with brown extremities and a gold head-orb||Bonded character's attacks do Ice damage.|
|Hayda||Rare||Dark green with a black stomach and a scarlet head-orb||Regenerates PP at the start of each combat round for all team members.|
|Jirna||Common||Yellow with grey extremities and a purple head-orb||Chao creates an earth shield to protect against damage.|
|Joy||Rare||Pink with scarlet extremities and a blue head-orb||Regenerates HP at the start of each combat round for all team members.|
|Kayla||Rare||Red/black with red horns and a green head-orb||Reduces the team's chance of being ambushed.|
|Keroyo||Rare||Green with light green extremities and a yellow head-orb||Increases odds of enemies fleeing from battle.|
|Knickt||Common||Gold with pale yellow extremities and a blue head-orb||Chao creates a shield of lightning to protect against damage.|
|Koolet||Common||Pink with pale purple extremities and a light blue head-orb||Bonded character is harder to hit.|
|Korus||Common||Orange with ochre extremities and a black head-orb||Chao creates a shield of fire to protect against damage.|
|Luunan||Rare||Pale yellow with an orange stomach, turquoise extremities, and a blue head-orb||Greatly increases the maximum PP of bonded character.|
|Oldarg||Rare||Red with a white stomach, scarlet extremities, and a dark green head-orb||Bonded character has a greatly increased chance to hit targets in battle.|
|Oolean||Common||Pale yellow with white extremities and a dark blue head-orb||Increases maximum PP of bonded character.|
|Ovus||Unique||Yellow with orange extremities, white stomach, and a magenta head-orb||Bonded character is automatically revived once during a battle.|
|Perty||Common||Dark green with light green extremities and a red head-orb||Chao creates a shield of water to protect against damage.|
|Pooki||Viral*||Ninja-style black with a black head-orb and red face||Bonded character takes less damage from enemy attacks and spreads the remaining damage evenly among other team members.|
|Pyraz||Common||Red with white extremities and a blue head-orb||Bonded character's attacks do fire damage.|
|Radu||Rare||Light blue with blue extremities, yellow stomach, and a black head-orb||Greatly increases the maximum HP of bonded character.|
|Rugle||Common||Pale pink with ochre extremities and a green head-orb||Bonded character has increased luck.|
|Seeri||Common||Purple with aquamarine extremities and a dark green head-orb||Chao creates a shield of wind to protect against damage.|
|Seggo||Common||Yellow with brown extremities and a purple head-orb||Bonded character's attacks do Wind damage.|
|Spartoi||Unique||Purple with mauve, cog-like facial markings, golden eyes, and a yellow head-orb||Bonded character's attacks may cause instant KO against enemies.|
|Stebsly||Common||Black with blue extremities and a pink head-orb||Bonded character regenerates HP at the start of every combat round.|
|Stilgin||Common||Red with dark red extremities and a white head-orb||Bonded character's attacks do Earth damage.|
|Stugs||Viral*||Ninja-style black with a black head-orb and white face||Bonded character is avoided by enemy attacks except as last surviving target.|
|Velk||Common||Light purple with pale blue extremities and a blue head-orb||Bonded character has increased resistance to damage.|
|Zimba||Common||Grey with pale orange extremities and a purple head-orb||Bonded character's attacks do Lightning damage.|
|Zousar||Rare||Yellow with pale blue extremities and a pale dirt-brown head-orb||Increases the team's chances of Ambushing opposing teams.|
|Sonic the Hedgehog (game series) characters|
|Heroes||Sonic (Super, Hyper, Darkspine, the Werehog, Excalibur) | Tails (Super) | Knuckles (Super, Hyper) | Amy Rose | Cream | Blaze (Burning) | G.U.N. Commander | Emerl | Silver (Super) | Marine | Shade | Lumina Flowlight | Chip | Shahra | Knights of the Round Table | Caliburn | Yacker | Sticks|
|Anti-heroes/ Neutrals||Shadow (Super) | Rouge | Espio | Charmy | Vector | Mighty | Ray | E-102 Gamma | Chaos (Perfect) | E-123 Omega | Bean | Bark | Jet | Wave |Storm | Merlina | Illumina|
|Villains||Dr. Eggman | Metal Sonic | Mecha Sonic (Super) | Metal Knuckles | Tails Doll | E-Series | Fang | Gemerl | Eggman Nega | Battle Kukku Army | Biolizard | Black Doom | Ix (Super) | Void | Iblis | Mephiles | Solaris | Dark Gaia | Witchcart | Erazor | King Arthur | Orbot | Cubot | Deadly Six | Lyric | Hard-Boiled Heavies | Infinite|
|Teams||Sonic/Heroes | Rose | Dark | Chaotix | Babylon|
|Other||Gerald & Maria Robotnik | Big | Chao | Tikal | E-101 Beta | Heavy and Bomb | Flicky | Animals|