Luigi is Mario's younger brother in the Super Mario series, and the sidekick of Mario as well. Despite being younger, he is still taller than Mario, and can jump higher than him as well. To play as him in New Super Mario Bros 2, hold the L and R buttons while selecting your save file to play as him.
Just like his brother, Luigi wears a similar hat to Mario's, except it is green, just like his shirt, and has the letter L (for Luigi) engraved in it. He, as well as Mario, has a long black moustache, blue eyes and a long nose. However, another difference, a less common one, from him and his brother is that his brown sideburns are noticibly longer than Mario's. He wears a green shirt, and a blue overshirt.
Luigi is portrayed as the taller, younger brother of Mario, and he is usually seen dressed in green with overalls. Although Luigi is a plumber, like his brother, other facets of his personality vary from game to game. Luigi always seems nervous and timid but is good-natured and not as quick to anger as his more famous brother. A baby version of the character named Baby Luigi debuted in Super Mario World 2: Yoshi's Island, who is held captured by Kamek. He also appeared in Mario & Luigi: Partners in Time as a playable character along with Baby Mario. He is voiced by Charles Martinet, just like his adult self.
While it has not been made official, Daisy may be Luigi's romantic interest. They were a romantic couple in the Super Mario Bros (film) and in Mario Kart Wii they are seen in statue dancing together. She was his caddy in NES Open Tournament Golf as Peach was to Mario. Also on Daisy's trophy in Super Smash Bros Melee, it says that she is possibly Luigi's answer to Mario's Peach.