YouTube Video

This Saturn-era Sonic the Hedgehog never made it past this conceptual stage. Why? I'll let YouTube uploader AssemblerX explain.

"This is a video of the concept "nights" version of Sonic Xtreme for Sega Saturn. Looking to produce a concept for a 3D sonic, a Sega USA team either used or closely followed the design of "Nights" and caused problems internally at Sega. Thinking or knowing that the US team had used their engine, the Japanese nights team had a fit. The engine was scrapped and a different engine, the so called "fish eye" version was used. This engine was later canceled as unworkable."

There's not much to it, but it looks at least somewhat workable from my perspective.