Mario, the mushroom-addicted jumpy-happy Italian plumber was created (or designed) out of technical limitations.

In the always insightful Iwata Asks series, creator Shigeru Miyamoto reveals how Mario came into life.

First of all, this is the final design (remember, it was the dot-graphics era of early 1980s).

According to Miyamoto, the parts were designed as follows:

• Mustache: was drawn to avoid drawing mouth, which could have consumed extra vertical dots.
• Eyes: were given two vertical dots to make him "cute". 
• Cap: was added to again, avoid drawing hairs which could have become complicated when Mario was in action (all the time) when his hair had to wave. Also the cap reduced the number of vertical dots – we can notice that above his eyes, Mario has only two dot-width. In real life he is literally a brainless person, but here magically no one notices.
• Jumper suit: Miyamoto wanted to highlight Mario's arms when he was moving to add the "running" effect. The logical solution was to separate the color between his arms and his torso. Is there such clothes? Yes – a jumper suit! Wait, the Donkey Kong game is situated in a construction site! A construction worker trying to rescue the princess from the evil gorilla! It works!
• Huge hands (or gloves): again, made bigger to highlight the arm-waving motion when Mario was running or jumping.

…Almost everything about Mario was created out of technical restrictions or gaming specifications. He was given the name Mario only because the result resembled Nintendo US Office's landlord Mario Segale, an Italian American so much. From Wikipedia:

During localization of the game for American audiences, Nintendo's warehouse landlord Mario Segale confronted Nintendo's Minoru Arakawa, demanding back rent. Following a heated argument in which the Nintendo employees eventually convinced Segale he would be paid, they opted to name the character in the game Mario after him.

Creating a long-lived device out of limited resource and existing technologies is what Nintendo does better than almost anyone in the world, and from Mario we can see it also applies to game characters.