Sonic Jam
"Sonic Jam" is a compilation which contains the four main "Sonic the Hedgehog" games released on the Sega Genesis: "Sonic the Hedgehog", "Sonic the Hedgehog 2", "Sonic the Hedgehog 3", and "Sonic & Knuckles". Unlike future "Sonic" collections, "Sonic Jam" does not use a Genesis emulator; the games are proper ports, and all are nearly identical to the original Sega Genesis releases, with the exception of minor bug fixes. "Sonic Jam" emulates "Sonic & Knuckles" "lock-on technology"—a special feature that allows the player to merge elements of "Sonic & Knuckles" into previous games, resulting in changes to the level design as well as the choice to play as Knuckles the Echidna in "Sonic the Hedgehog 2" and Tails in "Sonic & Knuckles".
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.