>>528202045
The Adventure 1 & 2 adaptations draw from a -lot- of material that ultimately went unused in the games. We know about some of it due to dataminers finding dummied-out data (the name of Amy's birdie, several deleted SA2 voicelines), and some of it is theoretical dropped plotpoints we can guess at (some material alluded to in Japanese guidebook, like the implication that the Shadow in SA2 might not be the actual Shadow, which wad replaced by the android subplot).
Some people think Series 2/Season 3 drew from canned material for Shadow 05 or Sonic 06.