When Sonic the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna arrived at a locale Chao Garden, they started to interact with the Chao they met there. One of the Chao there ended up inheriting Sonic's speed, prompting Sonic to name it Chronic.
Some time after, Dr. Eggman showed up under the assumption that their were magical items in the area. However, he would be disappointed when finding out there was not. Thus, he went on to destroy Chronic's home, forcing it and the rest of the Chao to move to the Lake of Rings.
Like most Chao, Chronic displays a cheerful and welcoming nature to Sonic. Upon inheriting the hedgehog's traits, he appears to have a more confident personality.
Powers and abilities
As a Chao, Chronic can gain the traits of creatures to which it is exposed to as it grows, like when it took on Sonic's traits. Once Chronic nears the end of its life-cycle, it can envelope itself in a cocoon and emerge as an egg—reborn as a new Chao with the traits it had in its past life. It is as well capable of flight.
Having taken on Sonic's abilities, Chronic is capable of running at super speed.