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 Blast
"Sonic Blast" was released worldwide in November 1996, and in Japan as part of the Kid's Gear brand on December 13, 1996, retitled "G Sonic". Worldwide, it was the last Sega-published Game Gear game; it was the system's final game outright in Japan. Though it has a similar title and was released around the same time, "Sonic Blast" and "Sonic 3D Blast" have little in common. The game is fairly common in North America, but "G Sonic" is extremely rare, costing almost 350. A port of the game was released for the Master System exclusively in Brazil in December 1997, distributed by Tectoy. The game had to be simplified to run on the Master System because of its lower graphical quality. Like "G Sonic", the Master System version of "Sonic Blast" is rare.