That channel must be owned by a former Travelers Tales employee, it has prototype footage for many of their older Genesis/ Mega Drive games, as well as beta footage of Sonic R.
Sonic 3D Blast prototype featuring a working two player split screen mode:
https://www.youtube.com/watch?v=qH4eZcTmVM4
Puggsy prototype footage:
https://www.youtube.com/watch?v=gybRLaWXGDo
Mickey Mania 2 cancelled prototype:
https://www.youtube.com/watch?v=iBEA9KmPw1I
The Legend of Galahad/ Leander prototype:
https://www.youtube.com/watch?v=D-H1vhXr1qU
Toy Story 3D FPS level prototype:
https://www.youtube.com/watch?v=XujWtRYtm3g
CODING SECRETS! How Toy Story's 3D levels were programmed:
https://www.youtube.com/watch?v=IhMMK3QLxSM&t=321s
Toy Story - Genesis highlight and shadow mode explained:
https://www.youtube.com/watch?v=cVSM92CBGmc
SEGA Genesis/ Mega Drive MEGADEMO -showcases graphical effects used in various TT games:
https://www.youtube.com/watch?v=zEBDwP9DRds
Really awesome stuff!
Uploaded today: earliest prototype of Sonic R on the Saturn:
https://www.youtube.com/watch?v=GEl508T02qY *yeah unrelated to the thread, but cool anyway)