Sonic the Hedgehog CD [Model G-6021]

Sonic the Hedgehog CD was released on September 23, 1993 (Thursday) in Japan. It is known outside Japan as simply Sonic CD.

The sonic team built Sonic CD using the original Sonic the Hedgehog code as a base, the game itself was conceived as an enhanced port of Sonic 2 for the Mega CD. At this point, it was codenamed Super Sonic and would feature additional levels, a fully orchestrated soundtrack, sprite-scaling effects, and animated cutscenes.

Meager sales of Sonic 2 in Japan and the team having its own vision resulted in the reworking of the port. It was titled CD Sonic the Hedgehog first before being renamed Sonic CD. Ohshima does not consider Sonic CD a sequel to the previous two Sonic games, although artist Yasushi Yamaguchi said players may assume that its story is set between Sonic the Hedgehog and Sonic 2.

Sonic CD marks the debuts of Amy Rose and Metal Sonic, both designed by Hoshino. Although Hoshino created Amy's in-game graphics, many staff members contributed ideas to her design. Her headband and trainer shoes reflected Ohshima's tastes while her mannerisms reflected the traits Hoshino looked for in women at the time. Hoshino designed Metal Sonic in response to Ohshima wanting a strong rival for Sonic. Hoshino had a clear image of Metal Sonic in his mind from the moment he was briefed, and his design emerged after only a few sketches. The character graphics were created using Sega's proprietary graphics system for the Mega Drive, the "Sega Digitizer MK-III", featuring a bitmap and animation editor. The team mostly used Macintosh IIcis. Graphics data was stored on 3.5-inch floppy disks, which were handed to the programmer to work into the game.

Ohshima cited Back to the Future as an influence on the time travel. Ohshima hoped for the time period to change instantly with a 'sonic boom' effect, but the programmers argued this was impossible and produced a loading sequence instead.

Sega did not pressure the team developing Sonic CD as much as the one developing Sonic 2. Ohshima felt this was because Sonic CD is not a numbered sequel; he considered it a recreation of the original game.