AM8 developed ideas for characters , an engine , and gameplay mechanics . Development emphasized speed , so AM8 eliminated character designs not associated with fast animals , as well as fast creatures like kangaroos and squirrels . One idea , a rabbit able to grasp objects with prehensile ears , showed promise at first but was too complex for the available hardware . The team narrowed its search to animals that can roll into a ball , their idea for an attacking move . Designers then realized that this would not seem aggressive enough , so they focused on two animals with spikes : armadillos and hedgehogs . The hedgehog character , first proposed by Naoto Ohshima , prevailed , although the armadillo would later become the basis for Mighty the Armadillo ( who first appeared in 1993 's SegaSonic the Hedgehog ) . Ohshima has admitted since that he created Sonic 's basic design by combining Felix the Cat 's head with Mickey Mouse 's body .