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.
Coleco Sonic
The Coleco Sonic is a handheld game console released in 2006 by Coleco Holdings, also marketed as PlayPal in Canada and the United Kingdom and Pocket Gear in Europe. It features 20 built-in games from the Master System and Game Gear. All the games can be played either on the integrated 2.4" TFT LCD display, or output to a TV via composite video. Its name references the Sega mascot, Sonic the Hedgehog, who stars in some of the games. The system comes with a power adapter, but can also use 3 AAA batteries as a substitute.