This was actually found a while back, but has been private till now:
Whole lot of neat stuff in here, including the rolling balls from GHZ, footage of Sonic's end of level animation, and a very sped up Robotnik boss music, UFOs in marble zone, spinning spikes in Spring Yard Zone, no drowning music, entirely different special stage layouts, etc.
Lots of other early Sega prototype footage, too, like Streets of Rage.
Whole lot of neat stuff in here, including the rolling balls from GHZ, footage of Sonic's end of level animation, and a very sped up Robotnik boss music, UFOs in marble zone, spinning spikes in Spring Yard Zone, no drowning music, entirely different special stage layouts, etc.
Lots of other early Sega prototype footage, too, like Streets of Rage.