Luigi is a tall, lean Caucasian man, who sports a skinny body and limbs. This is a stark contrast to Mario, who is short and slightly plump. Luigi wears a green shirt underneath his overalls, and he also wears the same gloves and shoes as his brother. His hat is also green, sporting the letter "L" in his namesake.
His facial features are considerably different compared to Mario's. His eyes are the same shade of blue, but his eyebrows are much more slim. His hair is also the same hue of brown, albeit it is slightly shorter than Mario's. Luigi's nose is also slightly larger and longer than Mario's. The most notable difference is Luigi's mustache, which strongly resembles stereotypical French mustaches, in comparison to Mario's bushy one.
Super Mario 64 Rumors
In 2000, a rumor spread up on SM128C.com. It stated, that the statue in the fountain had a secret message reading "L Is Real 2401" or "Luigi is Real Feburary 4th 2001". Altough the rumor had been spread earlier, the site was the first major source to mention it. Actually, Feburary 4th, 2001 is the date the last Nintendo 64 game, Paper Mario, came out. In this game, Luigi is existant.
Despite the rumors, no matter what players do, without hacks, having Luigi in Super Mario 64 and thus playing as him is impossible.
Super Mario 64 2
Since the N64 version was so successful, a sequel was planed for the Nintendo 64DD (64 Disk Drive) in 1999, titled Super Mario 64 2. The game was intended to have a two-player multiplayer game and Luigi was planned to appear in it. However, since the 64DD was a commercial failure, the game was cancelled.
Role in Super Mario 64 DS
In Super Mario 64 DS, Luigi is one of the characters trapped by Bowser's minions, along with Mario and Wario. Luigi is trapped by King Boo and Mario is needed to rescue him. Once Mario has 15 Power Stars, he can enter Big Boo's Haunt and go into the Luigi painting Big Boo Battle go through the doors where he hears King Boo's laugh, and defeat King Boo to free his brother. Luigi is needed to free Wario. Luigi must go into the mirror room with the Snowman's Land painting grab a Power Flower to go through the cage and enter the Wario painting, Chief Chilly Challenge. Once Luigi goes through the course and enters a hole, he must defeat Chief Chilly Challenge to rescue Wario. Like Wario, Luigi is optional to find. He has equal power to his brother, but moves a bit slower when carrying enemies. He has the fastest running and swimming capabilities and can scuttle-jump, which is similar to Yoshi's flutter-kick, but a bit lower. He can somersault and eve run on water briefly. When Luigi gets a Power Flower, he can turn invisible and walk through certain objects and enemies and won't get hurt, similar to Mario getting a Vanish Cap in the original. However, unlike Vanish Mario, Vanish Luigi can't go through ice.
- In the early days of the Mario series, Luigi was a recolor of Mario. This is especially noticeable in Super Mario Bros. and Super Mario Bros. 3.
- Luigi has almost always been able to do higher jumps and fall slowly. This started, when Yume Kōjō: Doki Doki Panic was re-branded and released in the US and Europe as Super Mario Bros. 2. The sprites being replaced with Mario characters, but their physics and abilties left intact, led to Luigi and Peach gaining their characteristic abilities for their own use.
- Luigi has the same last name as Mario, being Mario. Shigeru Miyamoto confirmed this saying Mario and Luigi's last names are "Mario"
- Luigi was celebrated extremely in 2013, also known as The Year of Luigi, which was Luigi's 30th anniversary.
 -the site where the rumors about L is Real 2401 began.