ArtStation - Sonic character sprites

Game Boy Advance - Sonic Advance 3 - Sonic the Hedgehog - The Spriters Resource

Custom / Edited - Sonic the Hedgehog Customs - Sonic (Sonic 2-Style, Expanded) - The Spriters Resource

NFG Games Presents - A Sonic the Hedgehog Sprite History

Custom Sonic Sprites (Original Palette) by MylesDeGreat on DeviantArt

Sonic Mania/Unused Graphics - The Cutting Room Floor

These edited Sonic 1 sprites are amazing!

The Real Life Sonic the Hedgehog in Sonic 2 sprite sheet! : r

Various Sonic sprites by Joschurale on Newgrounds

Kinda) Toei Sonic Sprites (V.2) by Welber13 on DeviantArt

Sonic Sprites image - stevethehedgehog - ModDB