Luigi

Luigi is Mario's slightly younger, taller fraternal twin brother and the deuteragonist of the. Throughout his life, he has lived in Mario's shadow, developing both cowardly and heroic tendencies. Despite this, Luigi has helped and fought alongside his brother on many occasions.  marks his first appearance in the Mario franchise and his debut in general. Originally an exact copy, then palette swap of Mario, Luigi was created to facilitate a second-player option. Since the two-player mode was dropped from most main Super Mario games beginning with , Luigi has gained his own identity and personality, becoming a co-starring character of the Mario franchise. This is especially noticeable in installments for the ' and ' series of games. Luigi's notable traits include his green cap, his smooth mustache, his cowardly personality, his Italian accent, his heavy use of power-ups, and a superior jumping ability to Mario.

The Doodle Demon comics
"Please don't a-say it."

- Luigi

Luigi's debut in The Doodle Demon franchise is in the comic Pasta, where he is a ghost since he died after falling into a pit of lava.

Super Mario Maker 3
Luigi appears Super Mario Maker 3 as a playable character. Luigi is given a builder outfit of his own, which is identical to Mario's but with dark green overalls. Luigi also appears in the game's Story Mode when the player fails a course twice and he offers to either complete the course for them, or parts to make the stage easier.

He also appears in two of the opening sequences. In the first opening, Mario, Toad, and Toadette walk towards the game's logo, notice the number "3" is missing, and when they hit it together, Luigi falls (with the number "3" landing on the logo) and they proceed to leave. In the second opening as of the version 1.1.0 update, Luigi is seen with a Key; once he arrives at the Key Door, Mario, Toad, and Toadette are there next to it and slowly approach Luigi, who then runs away with the Key, causing the three to chase him and take the Key by force off-screen. Afterwards Mario collects the Key and opens the Key Door, they proceed inside, and as the Key Door shuts, the number "3" falls on the logo.

Luigi's Super Mario Bros. Small form sprite may also appear if a Warp Door is knocked in the Super Mario 3D World style, akin to that game's Luigi sightings.

Character Luigi appears as an unlockable character power-up. The character can be unlocked either at random upon completion of an area in Remix 10 on Normal setting or harder, or by scanning a compatible Luigi amiibo. His appearance is based on that of Super Mario Bros., except with his modern colors. The character replaces some of the usual Super Mario Bros. sounds with sounds from Luigi's Mansion.