Luigi (ルイージ Ruīji?) is usually portrayed as the younger brother of Nintendo's official mascot, Mario. Luigi first appeared in the arcade game Mario Bros., where he was featured as a main character alongside Mario. Since his debut, Luigi has appeared in many games in the Mario series, most often accompanying Mario as a central protagonist, but has also starred as the main character in Mario Is Missing! and Luigi's Mansion. While Luigi was originally created as a character identical to Mario except for being colored green instead of red, his rise in prominence in the Mario series lead to the adoption of a personality and style of his own. He is normally depicted as cowardly, but when he does get the courage to step up, he can be tough and overcome his fears.
Although Luigi is a plumber, like his brother, other facets of his personality vary from game to game. In the Mario & Luigi series he is often portrayed as reluctant, cowardly and timid, whereas the Paper Mario series makes him a more laid-back, but still somewhat cowardly, personality who tends to embellish his own accomplishments and abilities in the hopes of sharing some of Mario's fame. He also tends to be more willing to help with Mario's quest, but does not get the opportunity to do so until Super Paper Mario. In Luigi's Mansion, he was still depicted as cowardly but manages to face his fears to save his captured brother.
In most of his video game appearances, Luigi's abilities are either identical to those of Mario or with slight variations. Since Super Mario Bros., Luigi and Mario have made extensive use of items to extend their abilities, such as the Super Mushroom, which allows the player's character to grow larger, the Fire Flower, which allows him to throw fireballs (in recent games, Luigi launches green fireballs), and the Starman, which grants Mario or Luigi temporary invulnerability.
In Super Mario Bros.: The Lost Levels (originally released in Japan as Super Mario Bros. 2), Luigi is distinguished as being a better jumper than Mario, but has lower traction, making the character more difficult to control. In Super Mario Bros. 2 (later released in Japan as Super Mario USA), Luigi is again the best jumper, although he is not as fast as Mario. The traction characteristic also appears in Super Mario 64 DS, where Luigi can run across a small amount of water with a running start using this power. However, he has a lower speed than Mario and is less agile than the other characters and, unlike Mario, cannot perform a wall-kick.
In Super Mario Galaxy, Luigi runs faster and jumps higher than Mario, but yet again has lesser traction.