I may have gone too far in this one... https://www.youtube.com/watch?v=S3aPiTEMxOA

A Bit of Sonic Fan Game History mainly from the 1990s and 2000s https://youtu.be/2GE2ZsluVwg

New info on Tails' Creation!!!!!!! https://youtu.be/nHuDtRK4JoU

Sonic made Cameo Appearances in several Anime.

https://youtu.be/AqMjfjySzys

Did Sonic Colors use the Hedgehog Engine?

https://youtu.be/m9L_hUkF1e4

Why Super Sonic can't use insta-shield in Sonic 3 https://www.youtube.com/watch?v=ywsg2fyhQnM

A bit on Sonic Rush's Development https://youtu.be/xVS3g3JjJeQ

High Level Overview of Classic Sonic Physics https://www.youtube.com/watch?v=SUmqMixephg

Fun & Insightful Tweets from Naoto Ohshima, Sonic's creator. https://youtu.be/fpfrfcIqx1A

Over 20 minutes on Sonic Generations Development

https://www.youtube.com/watch?v=MQdN3_YdM1A