How did this game come out only a month after Sonic the Hedgehog? http://www.gamefaqs.com/nes/587095-armadillo/data
It says 8/09/91 and Sonic was 7/26/91, so not even a month. Spies? Or they had the same idea, coincidence? Or early preview shots?
Video of it: http://www.youtube.com/watch?v=Up2Q14fZdeI
In this article Hirokazu Yasuhara is asked about why they were considering an armadillo rather than a hedgehog, but he doesn't answer:
(Special thanks to Stan S on Gamefaqs for writing a review of this game).