Mario

Mario is the main character from Nintendo's Mario universe who appears in several Press Buttons 'n Talk lets plays. He appears in Paper Mario, Mario Party 3, Mario Party Advance, Super Smash Bros, Mario and Sonic at the Olympics, New Super Mario Bros U and Mario Super Sluggers.

Paper Mario
Mario is the protagonist of Paper Mario.

Mario Party 3
In Mario Party 3, Mario is one of the opponents that Wario faces in story mode. He is shown to be very dumb, and obsessed with eating things. At one point he decides to eat a Poison Mushroom when he's 3 spaces away from the star, and rolls a one, thereby allowing Wario to get the star instead of him. This has been canonized not as an act of mercy, but simply as an illustration of how Mario's desire to eat things is more powerful than anything else, even the desire for stars.

Princess Peach
In the Paper Mario continuity, Mario and Princess Peach are shown to be in a relationship. They reportedly have a very intense sex life, which Mario enjoys detailing to numerous people. They seem to genuinely care for each other and Mario would do anything to save Peach from the clutches of the evil Bowser.

In the Mario Party continuity, Princess Peach is in a relationship with Mario only in Story Mode, where she makes him wear a Bowser suit and calls him Bowser whenever they engage in intimate relations, which Mario doesn't seem to understand. This indicates that they may have some relationship issues that they need to work out. Later, in Party Mode, it is said that Peach is in a relationship with Princess Daisy.

Luigi
Mario and Luigi are brothers, but Mario seems to think that Luigi is rather useless, and Luigi is resentful of all the adventures his brother has without him.

Goombario
Goombario the Goomba kid is the very first person to join Mario's party in Paper Mario. Mario considers him to be an annoying little scrub and has nothing but contempt for him, spending his college fund on a spell from Merlee. Goombario lives in Mario's pocket, so it hurts when Mario does a ground pound. Mario, of course, does not care. He makes many jokes at Goombario's expense and after getting new party members, almost never takes him out again except to mock him.

House Toad
"'Hey, if I don't come back...You were a nice guy.' -Mario"The Toad who runs the Toad house in Toad Town in Paper Mario has a unique relationship with Mario. At first, their relationship is antagonistic: Mario does not let anyone else use the Toad house, and there is often a line of people waiting outside the door. Toad often makes passive-aggressive comments imitating Mario.

However, they eventually become close friends. Toad opens up about his divorce and apologizes to Mario; he had just been drinking and going through some hard times. Mario, in a rare, kind moment, accepts the apology. Toad eventually offers Mario a nap free of charge (even though the Toad houses are already free) and invites Mario to his place for a longer conversation.

Yoshi Island Leader
Mario hates the leader of Yoshi Island in Paper Mario. No clear reason has been given as to why he started hating him, but their relationship is not helped by the fact that he prevents Mario from accessing a star piece by standing on it.

Trivia

 * For the entirety of Paper Mario, Mario might be in a coma. This is hypothesized by Alex and SungWon, but never actually confirmed. #comatheory
 * Despite his outfit, Mario's favorite color is actually blue. He hates the color red, but is colorblind and cannot tell that he wears it everyday.
 * For the entirety of Mario Party 2, Mario was hanging out with Yoshi, because no one invited him.
 * Mario's favorite anime is Naruto.
 * His Doctor alter-ego, Dr. Mario, doesn't actually have a PhD, he just started practicing one day. He has killed several patients.