Chao (Sonic the Hedgehog)

A Chao (チャオ) is a fictional life form in the Sonic the Hedgehog video game series published by Sega. Chao made their first appearance in the 1998 Dreamcast game Sonic Adventure as digital pets. They have since appeared in several video games in the Sonic the Hedgehog series as digital pets, minor characters, and gameplay elements. They have also appeared in games outside the series, and the Sonic X anime. Chao have been featured in promotions and merchandise, and generally well-received by critics such as IGN and GameSpot.

Conception and characteristics
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". A Chao "socialization program" was incorporated into Sonic Adventure 2 in order to make the game unique.

Chao are small creatures with a pudding-like body and behave much like human infants, with pleasant and relaxing personalities. Professor Chao, a minor character in Sonic Adventure 2, states that Chao are cute, and enjoy toys and being held or petted. However, they dislike being held while the player jumps, spun around, or thrown. Chao's diets consist of tree fruit and coconuts. Chao hatch from eggs found in Chao Gardens. When the player spends enough time with a Chao in the Chao Garden, the Chao develops a cocoon; it hatches from this as an adult. Eventually it develops another cocoon. If the Chao has been treated well, the cocoon is pink and the Chao is reincarnated as an egg; the cycle then restarts and the Chao remembers the player. If, however, the Chao has been treated poorly, the cocoon is gray and disappears. Chao can breed to produce fertile eggs.

Appearances
Chao have appeared in numerous Sonic the Hedgehog video games as digital pets. They made their first appearance in the 1998 Dreamcast game Sonic Adventure. The player can raise them, enter them in races, and export them to Chao Adventure, a game for the Dreamcast's VMU peripheral. The player can also trade Chao or post their high scores online using the Dreamcast's Internet capabilities. The Chao raising feature was expanded in Sonic Adventure 2; Chao may become "Hero Chao" or "Dark Chao" depending on whether the game's "hero" characters (Sonic the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna) or "dark" characters (Shadow the Hedgehog, Doctor Ivo Robotnik, and Rouge the Bat) are nicer to them. Chao can enter karate competitions in this game, as well as racing. The Game Boy Advance (GBA) games Sonic Advance, Sonic Advance 2, and Sonic Pinball Party feature a "Tiny Chao Garden", similar to the Chao Gardens of Sonic Adventure and Sonic Adventure 2 but with minigames in place of racing and karate competitions. Chao can be traded between Sonic Adventure 2: Battle and Sonic Adventure DX: Director's Cut—Nintendo GameCube ports of Sonic Adventure 2 and Sonic Adventure—and the GBA games featuring a Tiny Chao Garden.

Chao have also appeared in the series as minor characters and gameplay elements. Two Chao—one Normal and one Dark—who drive Chao-styled mechas are playable characters in the two-player battle mode of Sonic Adventure 2: Battle. On the Sonic the Hedgehog-styled pinball board in Sonic Pinball Party, one of the player's objectives is to hatch several Chao eggs. Each world in the 2004 GBA game Sonic Advance 3 features Chao-inspired minigames to earn extra lives for the player, and a sidequest that involves finding Chao to obtain Chaos Emeralds. 2007's PlayStation Portable installment Sonic Rivals 2 hides Chao throughout levels to be found in a free play mode. In the 2008 Nintendo DS role-playing game Sonic Chronicles: The Dark Brotherhood, Chao eggs are hidden throughout the in-game universe for the player to find and hatch. The resulting infant Chao can be equipped to characters. This affects the characters' performance in battle; for example, one kind will increase the character's hit points. The game features a multiplayer mode in which Chao can be traded between players who each have a copy of the game. Chao take the form of an item in the "Panel Flip" party game of the 2009 Wii and DS game Mario & Sonic at the Olympic Winter Games. Each player's object is to claim as many panels as possible in a six-by-six grid; finding a Chao upon flipping a panel claims all panels in a given row or column for the player.

Cream the Rabbit, a prominent character in the series, has a Chao named Cheese as a partner. In a move to keep her image safe, she often uses him to attack enemies instead of doing so herself. Other notable Chao include Chaos, a mutated Chao who serves as an antagonist in Sonic Adventure; and Omochao, a robotic Chao who appears in several games as a means of player tutorial.

Chao have also made appearances in video games outside the Sonic the Hedgehog series. In the 2004 PlayStation 2 game Sega Superstars; the player uses points earned during the game to please a pet Chao. Marking the introduction of the character Sonic the Hedgehog to the 2008 Wii game Super Smash Bros. Brawl, Chao and other characters from the Sonic the Hedgehog series appear as collectible trophies and stickers.

Chao were recurring characters in the Sonic X anime that ran from 2003 to 2006.

Promotion and merchandising
Chao have been adapted into mood key chains as part of a series of key chains based on Sonic X characters. Between July 27 and September 8, 2002, Sega hosted events at Tokyo-based department stores to promote upcoming Sega video games. Attendees could download "Chao Mini Garden"s and exclusive Chao to their copies of Sonic Advance. Chao clothing clips, along with accessories based on other Sega characters, were available.

Critical reception
Chao and the Chao raising system have been generally well-received by critics. In a review of Sonic Adventure, GameSpot's Peter Bartholow stated that "[w]ith the Chao-breeding simulation and the minigames, Sonic offers much more beyond the completion of its story." IGN stated that "SA more than has the extras department covered." This enthusiasm was extended to IGN's reviews of Sonic Adventure 2, Sonic Advance, and Sonic Adventure DX: Director's Cut. GameSpot's Shane Satterfield was critical of the Chao raising feature in Sonic Adventure 2: Battle, stating that "there's little in the way of interactivity" and that "the [C]hao training aspect using the Game Boy Advance is little more than a novelty." However, GameSpy's Shane Bettenhausen praised the feature in the game, comparing Chao to Tamagotchi digital pets. GameSpot's Frank Provo noted the appeal to "those people who might only enjoy pinball in passing" that Chao brought to Sonic Pinball Party. 1UP.com's Chris Baker called the Chao feature in Sega Superstars "ultimately worthless ... but some might find it amusing." Lark Anderson of GameSpot called referred to Chao as "hidden animal friends". In a review of Sonic Chronicles: The Dark Brotherhood, GameSpot's Shiva Stella praised the level of strategy that the game's Chao system added. Destructoid's Jim Sterling voiced a similar opinion, although saying that Chao had been "rubbish" in previous games.