 <unk> developed ideas for characters , an engine , and gameplay mechanics . Development emphasized speed , so <unk> eliminated character designs not associated with fast animals , as well as fast creatures like <unk> and squirrels . One idea , a <unk> 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 . <unk> then realized that this would not seem aggressive enough , so they focused on two animals with spikes : <unk> and <unk> . The <unk> character , first proposed by <unk> <unk> , prevailed , although the <unk> would later become the basis for Mighty the <unk> ( who first appeared in 1993 's <unk> the Hedgehog ) . <unk> has admitted since that he created Sonic 's basic design by combining Felix the Cat 's head with Mickey Mouse 's body . 
