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".
Sonic Chaos
Sonic Chaos is a platform game developed by Aspect and published by Sega. The game was released for the Master System in October 1993, and for the Game Gear the following month. The Game Gear version was re-released in 2003 as a hidden game in "Sonic Adventure DX" for the GameCube and Windows and as an included game in "Sonic Mega Collection Plus" on the PlayStation 2, Xbox and PC. In 2009, the Master System version was released on the Virtual Console.