A running gag in the series is that Luigi is abused and humiliated. When not being physically attacked, Luigi is often the victim of verbal abuse, including accusations of homosexuality. However, he can also provide comic relief due to being the butt of so many jokes.
Originally, Luigi looked like a retexture of his brother Mario, just like many other characters in SMG4's videos. However, beginning on March 7, 2016, his appearance changed to match his current look in the main Nintendo canon, but still as a Super Mario 64 sprite.
Luigi is kinder and more understanding than most of the other characters. He is often cheery, enthusiastic, fun, and ready to lend a helping hand. His main weaknesses are his cowardice, in which he gets very nervous when doing something dangerous or immoral, and his easily-exploited kindness, which often results in him being treated like a doormat.
However, when pushed too far beyond the limit, he has been seen to get angry. On these rare instances, he can be very unrelenting and mean, though he usually reverts back to his normal personality when he calms down.
Luigi has often been accused of being gay. He usually denies this, but he has shown homosexual behavior many times. He was attracted to Daisy in The Adventures of Mario and Luigi - Ep. 4, Awkward Weddings and also watched naked men on SMG4's computer, so he may be bisexual.
- In "Crystal Funhouse", Luigi is called "Luigi Gaywalker", but it is likely that "Gaywalker" is referring to his role in Mario's Star Wars battle as opposed to being his actual surname. The line "No! I like being Gaywalker!" further supports this possibility.
- Luigi owns a Nintendo 64 (and a Nintendo 64DD).
- He apparently has a PhD, as shown in "Retarded64: A Dose of Dr. Mario"
- It's revealed in "Operation G.A.Y" that he wears female underwear (Princess Peach dress). This fact is showed many times in other episodes.
- In "Guards N' Retards: Prisoners" and in "SwagQuest", Luigi is seen driving a kart and making an angry face at the prisoners (to Mario in SwagQuest). This a reference to his "Death Stare" from Mario Kart 8, which is very popular on the Internet. The Music playing while luigi doing it is "Ridin'" from Chamilionaire.
- Apparently, Luigi doesn't have a big brain, as in the "Toadassass-ination," when Mario tells him to throw a bunch of Koopas at Toad, he instead protects them.
- In some bloopers the characters say that Luigi is a girl (though this might be a lie). In "Ssenmodnar 5 (WAT (shocked face) Edition)" one of the facts about Mario says that Luigi is actually Mario's sister and in Bowser and the nightmare stone Bowser says to Smg3 "I already zapped Mario and his sister" (Luigi).
- In SwagQuest, Luigi said that he was in love with Daisy.
- Luigi seems to have a thing for Luigi dolls, as in both Meet the Luigi and Mario Simulator Interactive, he's seen making out with one.
- He tries desperately to gain swag, as shown in "SwagQuest".
- Luigi sometimes wears grey overalls.
- Luigi wins by doing nothing in the episode DerpTV: Mushroom Kingdom's Got Talent. This is a reference to the popular "Luigi wins by doing absolutely nothing" meme.
- Luigi is a skilled dancer, as seen in the videos "Love for Luigi. (Valentine's Special) and Meet the Luigi." He's also a professional gambler, as shown in the blooper "Casino, Cards and Chaos."