A former artist who worked at Sega revealed a concept sketch for an unused character from Sonic Adventure's development. Sonic Adventure was the defining game that many fans think of in terms of the series leaping into 3D, along with it being one of the Sega Dreamcast's strongest titles. However, Sonic Adventure wasn't the first time that the franchise attempted a 3D platforming game, as there's a tumultuous history behind the game that many may not know about.