Nintendo has explained much of the mystery behind Mario’s design. The reason for his hat, overalls and mustache all branch from technical limitations. So why is he pudgy little plumber? Technical limitations strike again! According to Miyamoto, the collision boxes for gaming devices at the time could only be squares. Therefore, Mario was plumped out on the sides to fill the entire collision box. Miyamoto also explains that Mario’s face is so large due to the low resolution of the platform.
It’s almost impossible to even imagine what Mario would look like if he was created without these technical limitations. Almost every aspect of the plumber is due to this or that being too hard to do on the hardware.
Don’t ever change, Mario.
(Source: Iwata Asks)