Sonic Crackers

Knuckles' Chaotix is a side-scrolling platform game similar to earlier entries in the Sonic series. Unlike other Sonic games, players are tethered to a computer or human-controlled partner; the tether behaves like a rubber band and must be properly handled to maneuver through stages. There are five playable characters, each with their own unique abilities. Knuckles the Echidna can glide and climb walls; Mighty the Armadillo can perform a wall jump; Espio the Chameleon can run along walls and ceilings; Vector the Crocodile can boost through the air and climb walls; and Charmy Bee can fly and hover.

There are two other partner characters, Heavy the Robot and Bomb, who hinder players' progress due to their slow or destructive nature, respectively. The story takes place on a mysterious island and follows the group's efforts to stop Doctor Robotnik and Metal Sonic from harnessing the power of the island's mythical Chaos Rings to satisfy their evil deeds.

Although Sonic Team is sometimes credited for developing Knuckles' Chaotix, it was developed by another internal Sega team, including staff who had worked on Sonic CD (1993). Development began around April 1994 for the Sega Genesis as an engine test, with the working title Sonic Crackers. The prototype featured Sonic and Tails joined by an elastic band of energy; the name likely comes from clackers, a toy comprising two balls connected by string. According to the journalist Ken Horowitz, Sonic Crackers was most likely a ROM made to demonstrate new concepts to management. Some ideas were used in Sonic 3D Blast (1996), while the level design, tethering, and some music resurfaced in Knuckles' Chaotix.

Sega eventually moved development to the Genesis' more powerful 32X add-on. According to Horowitz, this was because the 16-bit era of consoles was coming to an end. Former Sega of America CEO Tom Kalinske recalled that Knuckles' Chaotix was once intended for the Genesis' successor, the Sega Saturn, as a mainline Sonic game. According to Kalinske, development moved to the 32X when it became clear that the game would not be ready for the Saturn launch; Kalinske said it was "too big, it was taking too long, it was over budgeted, it was behind schedule". Because Sega needed new 32X games, Sega decided to downsize the game and introduce it quickly on 32X.

Knuckles' Chaotix received mixed reviews, and failed commercially, as did the 32X.

The game's presentation divided critics. The four reviewers of Electronic Gaming Monthly (EGM) praised its graphics and believed the game was one of the best for the 32X, and GameFan considered Knuckles' Chaotix the best entry in the franchise since Sonic the Hedgehog 2 (1992). On the other hand, a reviewer from Next Generation found the graphics garish, and felt that the game made "unimpressive attempts to show off". GamePro, Game Players, and IGN believed the game failed to push the 32X to its limits, citing the lack of graphical effects and Genesis-quality audio, though IGN felt some elements, such as several musical tracks, were highlights. In 2008, GamesRadar wrote that Knuckles' Chaotix was the best game for the 32X and was underrated, though it still considered the game a "wasted opportunity".

Knuckles' Chaotix is considered the last of the "classic" Sonic games before the 3D game Sonic Adventure (1998) took the series in new gameplay directions. Several of its concepts were re-used in later Sonic games. A similar partner system features in the Game Boy Advance game Sonic Advance 3 (2004), and IGN noted similarities between the game's auto-running special stages and Sonic and the Secret Rings (2007). Two tracks from Knuckles' Chaotix, "Tube Panic" and "Door Into Summer", appear in Sonic Generations (2011). The "Hyper Ring" power-up re-appeared in Sonic Mania (2017) and a recreation of Knuckles' Chaotix's final boss fight was added in a 2018 update.

With the exception of Mighty, all Chaotix members have become recurring characters in the Sonic series. The characters initially did not reappear until Sonic Heroes in 2003. Director Takashi Iizuka said that Sonic Team revived the Chaotix because the studio thought they were unique and had never used them. Iizuka considers the Heroes version of the characters different from the 32X one, claiming to have created new characters simply using the same designs.