FUN FACT: while sonic team and sega where working on sonic 2 dic was working on the sonic cartoons and they wanted to include tails (but we didn't know what tails looked like at the time)so they asked for a picture of tails and they gave them the picture from the prototype that's why tails is brown in the cartoons.
"This Sonic 2 ROM hack restores many unused concepts of Sonic the Hedgehog 2 during development." Tails was originally brown in development, and the 90s cartoons used that in-development art for their character designs.
