Luigi (Super Mario Bros.)
Luigi is the younger twin brother of the world-famous Super Mario. He was first revealed to the public in 1983 with the release of Mario Bros., and has since gone on to star in his own games (such as Luigi's Mansion and Super Luigi U.)
While Luigi has existed for slightly less time than Mario, he has been subject to far more characterization and development. In the beginning, Luigi was simply a green Mario. His sprites were the same as Mario's, but the red was shifted to green. However, as the series has progressed, each character has had physical and emotional distinctions between each other. While Mario is portrayed as the classic, perfect hero that loves their adventure and the danger it comes with, Luigi is shown to be meek, shy, and easily scared. Regardless, he embarks on almost as many quests as Mario, risking his life all the same, and proving to be far more of a hero than Mario.