Sonic the Hedgehog
Due to the success of "Sonic" games on the Sega Genesis, the series was introduced to the Master System and the Game Gear. Sega began by releasing "Sonic the Hedgehog", a 2D platform game, in 1991. The game featured Sonic's ability to run and to jump at high speeds like its Mega Drive/Genesis counterpart but with notably different level design and music. Sega later released "Sonic the Hedgehog 2" another 2D platform game, in 1992. The game differed from its Genesis counterpart with different levels and music and by not including a "spin dash" maneuver. It also featured a different storyline in which Doctor Robotnik kidnaps Tails, who is non-playable in the Master System/Game Gear version. "Sonic Chaos"/"Sonic and Tails" (Japan), released in 1993, was similar to the earlier two Sega Master System/Game Gear "Sonic" games, but featured Tails as a playable character. A sequel, "Sonic Triple Trouble"/"Sonic and Tails 2" (Japan), a 2D platform game, was released in 1994 for the Game Gear and introduced a new character, Nack the Weasel, who, along with Knuckles and Doctor Robotnik, raced to collect the Chaos Emeralds. One of the last games for the Sega Game Gear, "Sonic Blast", was released in 1996 and featured prerendered sprites.
Knuckles' Chaotix
Development of "Knuckles' Chaotix" began in early 1994 as an engine test for the Sega Genesis dubbed "Sonic Crackers". Although Sonic Team is sometimes credited for developing the game, it was developed by another internal Sega development team including young members of the staff who had worked on "Sonic CD" (1993). Developed as an idea for the next "Sonic" game, the prototype featured Sonic and Tails joined together by an elastic band of energy. Development eventually moved to the more powerful 32X add-on for the Genesis. Sonic and Tails were replaced by a group of characters led by Knuckles the Echidna, but the core tethering gameplay was retained. The project was titled "Knuckles' Ringstar", and later "Knuckles' Chaotix". The "Sonic Crackers" prototype ROM image was later leaked online and can be played with emulators.