Main Four

The titular Quad Cast seen in every mainline Mario game, Mario, Luigi, Peach, and Bowser each play a crucial role in the overall plot.

Mario
The titular silent protagonist of the Paper Mario games, Mario is a daring and brave hero that is willing to lend a helping hand to anyone and everyone he comes across. His heart is pure and he is always willing to do things for the greater good. When it comes to friends, he is always willing to help them out and support them, even if his own opinions don't exactly align with their own, and is always willing to cheer them up and help them achieve what they want and need.

Luigi
Brother of Mario, Luigi is the more cowardly one of the two. On paper and tying into the Paper Mario interpretation of Luigi, he tends to exaggerate his previous adventures but when actually faced with the challenges he so exaggerated he tends to cower and become afraid. The reason he does is is due to the fact that he is secretly very envious of how much more recognised and brave his brother is, and desperately wishes that he was just like who his brother is. When having become much more acquainted with the other two, Luigi becomes much more playful and jokester-like as opposed to his more envy-coated boasting side, and is extremely caring and anxious, extremely alert and aware of his surroundings in terms of danger, and overall has a sweeter demeanour.

Peach
The titular Princess, Peach is a very dutiful and responsible princess who despises dirtying her royal position. When not being caring, she is incredibly smart and observant, and is able to spot small things that could be of incredible use in order to escape into a safer area. In the beginning, Peach acts more of a support but really wants to learn about how to be more confident in her fighting prowess in order to potentially defend herself in future critical situations, and when she learns this she starts getting more powerful offensive moves that allow her to hold her own when the situation comes to it.

Bowser
Usually the titular antagonist of the mainline series, Bowser finds himself in the occasional protagonist position once again. Naturally confident and boisterous, Bowser has a loud mouth and isn't afraid to speak what's on his mind. He is more brain than brawns and whilst powerful, can attack enemies without a second thought which can often land him in undesirable decisions due to his recklessness. Being a father and active leader of a large group of henchmen, Bowser has a lot of experience when it comes to giving others motivation even if he may have to take the person in questions down a few pegs in their ego; tough love as he calls it. Bowser strictly serves his antagonist role at first and didn't want to help protagonists, but as he spends more time with them he lowers that rule and begins enjoying his time hanging around them more, becoming more of a wild joker.