Why are Sonic's eyes green in Sonic Adventure, the franchise's first serious crack at a fully 3D polygonal platformer? It turns out there's a lovely little story behind that. Ristar creator Yuji Uekawa was the man tasked with revamping Sega's mascot for his debut on Dreamcast. Some of his decisions were practical: shrinking Sonic's enormous, swept-back skull and elongating his limbs, for instance, so that he doesn't look like a fuzzy joystick when viewed from the rear. Others were a touch more poetic. "He is always seeing these green pastures around him, like in Green Hill Zone," Uekawa explains in an interview conducted for Sega's 25th anniversary artbook. "I thought it would be nice to reflect that in his eyes."
Poor Sonic. Once a star runner rivaling Mario he went on to become as washed out a mascot as they come, subjecting himself to several of the worst platformers in the last decade with Sonic the Hedgehog (2006) and Sonic Unleashed - the latter of which cast him as a 'werehog' because he apparently didn't have enough misguided baditude already.
Just as he was about to fade into obscurity, he's seen something of a resurgence lately with both Sonics Colours and Generations. It's been a slight return to form, but still there was something missing. With 2D gaming back in vogue there was a demand for an entirely 2D HD Sonic game that could blend our memories of Sonic blazing through roller-coaster-like terrain with the snazzy new graphics of today.
When the highly awaited first numeric sequel to the franchise since 1994 arrived with Sonic the Hedgehog 4: Episode One, it was met with mixed reception. Its simplified design harkened back to Sonic's golden years, but the ropey physics left a sour taste with his long-standing followers.