Apparently, Super Shadow was originally supposed to be silver-colored in Sonic Adventure 2

There's apparently an unused texture in the…

Goomba - Super Mario Wiki, the Mario encyclopedia

Great Eastern GE-98960 Sonic The Hedgehog 13 Plush Doll, Silver : Toys & Games

Sonic Adventure 2 11x17 Print

What is your biggest sonic theory : r/SonicTheHedgehog

Sonic Adventure 2 Figure Revealed By S-Fire

Is there an official reason in the games why Shadow looks like Sonic or is it just a coincidence? : r/SonicTheHedgehog

Sonic Character Heights

Sonic Colors Remastered listed in portfolio of German voice-over studio [Update] - Gematsu

Shadow the Hedgehog (Game), VS Battles Wiki