Luigi

Luigi (full name Luigi the Sexy Plumber, also known as Luigi Gaywalker) is Mario's younger twin brother, and just like him, is an Italian plumber from the Mario franchise. Naturally, due to said status, he is one of the secondary characters in SuperMarioGlitchy4's bloopers.

A running gag in the series is that Luigi is frequently abused, made fun of, or otherwise humiliated throughout the series, especially by Mario himself. Often, he is physically attacked, although he's also the victim of verbal humiliation, occasionally by being accused of homosexuality. Due to this, he's often the comic relief character in the series.

Personality
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.

Appearances
While there's multiple bloopers in which he didn't appear in, Luigi has made many appearances in the series due to his role as a second character, typically taking the role of a comic relief.

Mario
Mario heavily abuses his brother Luigi, often insulting him, beating him up, and in early bloopers killing him for no reason, although he always comes back to life for some reason. Why Mario does this is unknown, but it may be because he resents Luigi for outperforming him; Luigi always beats him in Super Smash Bros, Mario Kart and Mario Party, and Mario gets very angry when Luigi out-jumps him in Long jump, causing Mario to overjump all the way out of Earth and into outer space. Luigi also gets angry at Mario when he is being too stupid.

Despite their rivalry, Mario and Luigi do seem to truly care for each other. This is especially apparent in Luigi's Retarded Mansion, when Luigi risks his life to rescue Mario.

Mario and Luigi's true relation is unknown. While they are usually said to be brothers (which is true in the official Mario canon), there are two conflicting account of Mario and Luigi's relation. In How Mario was Born, Mario gave birth to Luigi, and in The (TOTALLY ACCURATE) documentary of Mario, the two met at an orphanage.

SuperMarioGlitchy4
While he has sometimes called out on Mario for abusing Luigi, SuperMarioGlitchy4 very rarely has interacted with him, often hanging around with Mario instead. However, on the rare occasions that they do, SMG4 often treats Luigi in the same condescending manner most others do.

Toad
Toad, alongside Mario, looks down on Luigi. Though they don't usually interact, Toad often is condescending and mean towards him. However, while Mario tends to abuse Luigi in a physical form, Toad prefers to do so in a verbal method.

However in the blooper The Visitor 2014 Luigi shows that he actually cares about Toad, as he cries deply over his death (altrougth evrybody that were murderd by Enzo came back to life)

Daisy
Though she doesn't return his feelings, Luigi is in love with Daisy. He has occasionally tried to romance her, such as in The Adventures of Mario and Luigi - Ep. 4 and Awkward Weddings. Despite this, Luigi claims Daisy doesn't like him, which implies that it is the truth and/or Luigi got over Daisy. However the events of Mario 64: Love for Luigi (Valentine's Special) contradicts this.

Waluigi
While Waluigi is Luigi's self-proclaimed rival, he has only been seen antagonizing him during Ssenmodnar 9.

Trivia

 * 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).
 * 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.
 * Luigi doesn't have a big brain, as seen in "Toadassass-ination" when Mario tells him to throw a bunch of Koopas at Toad, but he instead protects them (as shown in the picture below).
 * It was revealed in "How Mario was born" that Mario actually pooped Luigi out, meaning that Mario is technically Luigi's mom but in "The (TOTALLY ACCURATE) documentary of Mario" the two meet in an orphanage.
 * On some bloopers the characters says that Luigi is a girl (Though this might be a lie) like 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 nitghtmare stone Bowser says to Smg3 "I already zapped Mario and his sister" (Luigi).
 * In SwagQuest, Luigi said that he was in love with Daisy, however he says that Daisy does not love him as he could have gotten over Daisy.
 * Luigi tries desperately to gain swag, as shown in SwagQuest.
 * Luigi sometimes have grey overalls.
 * Luigi has feelings for sexy men for what X said in Luigi's clothes in "Switcheroooveralls