Luigi

Luigi is the younger brother of Mario, often serving as the second player in most Super Mario games, though he can sometimes take a starring role, such as in the Luigi's Mansion series.

In the Shyrx Saga, Luigi sometimes appears as a major character.

Appearance
Luigi appears as a slightly taller version of Mario, with a green shirt, green hat, and darker overalls.

However, starting with Brotherly Things, Luigi now uses Cjes's model, which means he now looks more accurate to his official appearance.

Personality
Luigi is often shown as being timid and afraid of lots of things, such as in Mario is Missing where he freaks out by just by seeing a Chain Chomp, even though it was attached to a pole. Despite this, Luigi is often depicted as being a kind-hearted figure.

Mario
Being his younger brother, Luigi looks up to Mario and very much cares for him.

SuperRhys217
Luigi is a somewhat close friend to Rhys, though the two don't interact too often, the one exception being Mario is Missing.

UltraGamer8
Luigi was quite startled by UltraGamer8 looking similar to him, though he seems to have warmed up to it.

Story/History
Luigi has never had any truly important roles, being mostly a side character up until the timeline reset.

SuperRhys217 Generations
Luigi went with Mario, SuperRhys217, and SR217's past self to the past castle to try and stop the Zombie infestation. After tough battle, both of the Rhyses go inside the castle, while Luigi and Mario stay outside. Eventually, they get attacked by Darknar and his Dark Angels, but they manage to fend them off. Suddenly, a great big dark sphere starts to consume the castle, where the Mario brothers decide to flee. The timeline is then reset by Chrono.

Super Mario 64 Bloopers
Luigi is a part of the main cast, along with Mario, SuperRhys217, and UltraGamer8. He appears in nearly every blooper, often supporting the others in their endeavors.

World Traveler 64
Luigi, along with Toad and UltraGamer8, all search the castle for the missing SuperRhys217, but they find nothing.

Mario eventually comes back from Bomb-omb Battlefield and shows them to Uatarlovegames, who warns them all of shadow creatures coming to make all light expire. He then makes his leave, having Luigi and the others guard the castle while making preparations for what's to come.

Trivia

 * Before Brotherly Things, Luigi had a red M on his cap instead of a green L, as he used the same model as Mario.