Knuckles' Chaotix is a 1995 platform video game developed by Sega for the 32X. A spin-off from the Sonic the Hedgehog series, it features Knuckles the Echidna and four other characters known as the Chaotix, who must prevent Doctor Robotnik (Dr. Eggman) and Metal Sonic from obtaining six magic rings and conquering a mysterious island. Gameplay is similar to previous Sonic games: players complete levels while collecting rings and defeating enemies. Knuckles' Chaotix introduces a partner system whereby the player is connected to another character via a tether; the tether behaves like a rubber band and must be used to maneuver the characters. While Sonic Team is sometimes credited with creating Knuckles' Chaotix, it was developed by another Sega team. Production began with Sonic Crackers, a 1994 prototype for the Sega Genesis which experimented with the tethering system and featured Sonic and Tails. Knuckles' Chaotix was planned as a Sonic game for the Sega Saturn, but transitioned to the 32X when it could not be completed in time. Sonic and Tails were replaced by Knuckles and a group of mostly pre-existing characters; Mighty the Armadillo first appeared in the arcade game SegaSonic the Hedgehog (1993). Knuckles' Chaotix was released in North America and Japan in April 1995, and in Europe in June 1995. It received mixed reviews and failed commercially. Reviewers found the tethering physics cumbersome, although some appreciated it as an attempt to innovate. The level design and low difficulty level were also criticized. Journalists have described Knuckles' Chaotix as the last of the "classic" 2D Sonic games before the series moved to 3D. Some characters and concepts it introduced feature in later Sonic games and media. Despite interest from fans, it has not been rereleased beyond a brief period through GameTap in the mid-2000s.