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".
Ristar
Back in late 1994, Sega was originally pitching "Ristar" to be the successor of Sonic the Hedgehog. However, the game never received a ton of exposure or sales, mainly due to being released just three months prior to the Sega Saturn, Sega's successor to the Genesis, overshadowing it. In a 1994 "Electronic Gaming Monthly" interview, Sega marketing staff Lisa Best and Terry Tang claimed "Ristar" was not designed by the same "Sonic" programming team, although much of the game's staff would later go on to create "Nights Into Dreams" for the Saturn, the next game to be officially credited to Sonic Team. This, along with "Ristar's" inclusion in a number of "Sonic" themed compilations and re-releases in subsequent year, would lead game journalists to retroactively label the game as being developed by Sonic Team.