Ultimately, this concept was dropped in favour of a hedgehog - the rabbit ears proved too complex for Sega's 16-bit technology - though the design still faced stiff resistance from Sega's US office, where hedgehogs aren't indigenous fauna, or well known.
Sonic's human girlfriend - who as we see from the concept art above, would have been wracked with carnal cravings for Sonic - was called Madonna. She had been inspired by the popular singer of the same name, even borrowing Madonna's late-80s pixie cut. She later appeared as a much less overtly sexualised character in the Sonic the Hedgehog comic series.
Should Madonna have remained part of the series, it would have raised questions regarding the nature of her relationship with Sonic. Though sexual acts between humans and animals - providing they do not involve penetration - are legal in Canada, it is considered a crime by most countries around the world.
When Sonic consumes food, it travels to his stomach where acids break it down into simpler chemicals, which Sonic's body then absorbs.
The food which cannot be digested first passes to Sonic's small intestine, where any nutrients are absorbed further, and the remaining bulk then travels to the large intestine. Bacteria helps break down Sonic's food, and that which cannot be digested is released as feces, via his anus.
Indeed, the number of countries where Sonic could travel safely is limited. Hedgehogs are traded throughout Eurasia and Africa for medicine and witchcraft, while the Bedouin tribes of the Middle East believe hedgehog meat can cure arthritis. In Morocco, inhaling the burnt skin and spines of a hedgehog is considered a remedy for male impotence.
Other common health complaints that Sonic must be aware of include fatty liver disease caused by a bad diet, and ringworm.
Sonic's courtship ritual can last hours. If he is successful in impressing the object of his affections, she will lay down her spines, and allow Sonic to mount and penetrate her without injuring him. However, few female hedgehogs are a one-man sort of a woman - and Sonic will likely have to share her with a number of other potential suitors throughout the night.
Unfortunately, like all hedgehogs, Sonic is severely lactose intolerant. Drinking cow's milk gives him chronic diarrhoea, and if he is unable to temper his milk-lust, he could even die - quite literally pooing himself to death.