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 Sega Genesis games
Sega Meganet, also known as the Net Work System, was an online service for the Mega Drive in Japan. Utilizing dial-up Internet access, Meganet was Sega's first online multiplayer gaming service, and functioned on a pay to play basis. The system functioned through the use of a peripheral called the Mega Modem and offered several unique titles that could be downloaded, and a few could be played competitively with friends. In addition, it shared technology and equipment with more serious services such as the Mega Anser, used for banking purposes. Though the system was announced for North America under the rebranded name "Tele-Genesis", it was never released for that region.