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.
Sonic Mega Collection
According to the director, Yojiro Ogawa, the purpose of the compilation was to introduce younger players to the original games in the "Sonic" series. The games are played through a Genesis emulator developed by Sonic Team themselves. Outside of the games, the compilation includes Sonic-themed videos and illustrations, as well as high-resolution scans of the instruction manuals and "Sonic the Hedgehog" comic covers.