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.
ToeJam &amp; Earl
"ToeJam & Earl" received positive reviews, which Bill Paris of UGO described as "almost unanimous critical acclaim". However, Sega deemed it a commercial failure due to low initial sales. The game built a cult following through word of mouth, and it was further aided by the Sega Genesis's Christmas 1991 sales spike, caused by the release of "Sonic the Hedgehog". "ToeJam & Earl" was later considered a "cult" success. According to Ken Horowitz (2016, p. 74) author of Playing the Next Level: A History of American Sega Games, "In all, the game sold 350,000 copies for Sega, a remarkable feat for such an unconventional title on a fledgling console." "Entertainment Weekly" picked the game as the #9 greatest game available in 1991, saying: "Simply hilarious, from the Warner Bros. cartoon-inspired sound effects to the rap songs players can improvise while using the control pad. "