By now, we're sure you know the story of Sonic's original design. He used to have fangs, a human girlfriend named Madonna, and even a rock band. Turns out SEGA America thought this vision for Sonic simply wouldn't work on a worldwide scale, so they turned him into the character we eventually got with the original Sonic the Hedgehog game. Not surprisingly, the team behind Sonic's original iteration wasn't happy with these design changes. The blurb below comes from a Polygon interview with former SEGA of America CEO,Tom Kalinske.
“[I] think they resented the fact that we changed him from being aggressive, and having fangs and [a] very sharp personality — and to some degree a menacing personality — to being soft and friendly. I think they resented that. But I don’t know [if] I’d carry it so far as to why they didn’t do the things that should have been done. I think it might have been part of it, however.”