For the initial design of Sonic the Hedgehog, Naoto Oshima claims that he just stuck Felix the Cat's head on the body of Mickey Mouse. He was surprised, later, that no one at SEGA noticed.

The majority of these games features Sega's icon, Sonic, though a few other Genesis gems are included to round out the deal. The youthful blue hedgehog was once more recognizable than Mickey Mouse ...

Sega will bring games starring Mickey Mouse, Sonic the Hedgehog and soldiers old and new to E3 2013, according to a post on the Sega Blog.