The Chaotix are a group of fictional characters in the Sonic the Hedgehog series of video games. They debuted in the game Knuckles' Chaotix (simply called Chaotix in Japan). The group, or individual members in it, has since appeared in Sonic the Fighters, Sonic Heroes, Shadow the Hedgehog, Sonic Rivals 2, and Mario & Sonic at the Olympic Games. The character Mighty actually made his debut appearance prior to Knuckles' Chaotix, in SegaSonic the Hedgehog.

They have also appeared in many other Sonic continuties, including several Japanese Sonic manga, the American Sonic the Hedgehog comic series, the British Sonic the Comic comic series and the Sonic X anime series and tie-in comic.

In virtually all of their incarnations the Chaotix are presented as a somewhat dysfunctional group. They are often used in stories to add a sense of comedy to otherwise serious situations. In Sonic X, Team Chaotix seem to be able to see beyond the fourth wall, adding to their humorous image.

Source: Wikipedia