Introduction Among Sonic fans, Sonic CD (1993) occupies a unique space. Developed by Sega’s Sega CS (with major contributions from Naoto Ohshima and Kazuyuki Hoshino), it was the first Sonic game on a CD-ROM format. That meant Redbook audio, anime-style cutscenes, and a larger storage capacity. But for decades, Sonic CD was also one of the least hacked Sonic games—until the late 2010s. Unlike Genesis ROM hacks (which have thrived since the 1990s), Sonic CD ROM hacks require a different skillset: unpacking ISO files, understanding the Mega-CD’s unique hardware (subcode, PCM, BRAM), and repurposing assets without breaking the game’s delicate CD streaming logic.