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.
Sega Genesis
In mid-1990, Nakayama hired Tom Kalinske to replace Katz as CEO of Sega of America. Although Kalinske initially knew little about the video game market, he surrounded himself with industry-savvy advisors. A believer in the razor and blades business model, he developed a four-point plan: cut the price of the console, create a U.S.-based team to develop games targeted at the American market, continue and expand the aggressive advertising campaigns, and replace the bundled game "Altered Beast" with a new game, "Sonic the Hedgehog". The Japanese board of directors initially disapproved of the plan, but all four points were approved by Nakayama, who told Kalinske, "I hired you to make the decisions for Europe and the Americas, so go ahead and do it." Magazines praised "Sonic" as one of the greatest games yet made, and Sega's console finally took off as customers who had been waiting for the release of the international version of Nintendo's Super Famicom—the Super Nintendo Entertainment System or SNES—decided to purchase a Genesis instead. Nintendo's console debuted against an established competitor, while NEC's TurboGrafx-16 failed to gain traction, and NEC soon pulled out of the market. In large part due to the popularity of "Sonic the Hedgehog", the Sega Genesis outsold the SNES in the United States nearly two to one during the 1991 holiday season. This success led to Sega having control of 65% of the 16-bit console market in January 1992, making it the first time Nintendo was not the console leader since December 1985.