Sonic the Hedgehog
The Sega Genesis had "add-on" systems that incorporated "Sonic" games. "Sonic CD", released for the Sega CD, was a 2D platform game released in 1993. The game introduced the characters Amy Rose and Metal Sonic and featured levels that differed depending upon whether Sonic was in the past, present, or future time frames. "Knuckles' Chaotix", a spin-off released in 1995 for the Sega 32X, featured Knuckles and a new group named Chaotix fighting against Dr. Robotnik. The game featured a two-player cooperative system in which the on-screen characters were connected by magic rings. There was also "Sonic Eraser", a puzzle game released exclusively on Sega Game Toshokan in 1991.
List of 32X games
The 32X is an add-on for the Sega Genesis video game console. Codenamed "Project Mars", the 32X was designed to expand the power of the Genesis and serve as a holdover until the release of the Sega Saturn. Independent of the Genesis, the 32X used its own ROM cartridges and had its own library of games. A total of 40 titles were produced worldwide [36 NA games ("10 Exclusives"), 27 PAL ("2 Exclusives"), 18 JP ("1 exclusive"), and 1 game "exclusive" to BR], including six that required both the 32X and Sega CD add-ons.