Board Thread:General Discussion/@comment-24553409-20140429164602/@comment-477304-20140430025351

Mighty isn't Sonic prototype, that's a common misconception.

When Sega was coming up for ideas for their mascot, it came to a toss up between making the character a hedgehog or an armadillo as they are both animals that can curl into balls, but it was decided that the character would be a hedgehog. The character wasn't designed until he was a hedgehog as best to my knowledge, unlike the other candidates, such as the man in pyjamas (who later became Robotnik), a rabbit, and even a shameless Mario rip-off, I have not seen any concept art for an armadillo character. However the armadillo concept was picked up for Mighty after Sonic was designed.