Protagonists
Mario
- Adaptational Jerkass: He's much more abrasive than his canon counterpart, what with constantly quarreling with his brother Luigi, occasionally getting irritated with rescuing Peach, and having a deep hatred for Diddy.
- Deadpan Snarker: Maybe not as much as his brother Luigi, but he does provide some quips.
- Death Faked for You: In "The Day Super Mario Died", Luigi decides to steal the spotlight from him by throwing him off a hill and making everyone believe he died. Even he believes his death when Boo tells him, but they both eventually find out that Luigi lied.
- Gleeful and Grumpy Pairing: He's the bitter Grumpy to his brother Luigi's Gleeful.
- Jerk with a Heart of Gold: He may be an absolute jerk to everyone, but he still does what he believes is right.
Luigi
- Adaptational Jerkass: Downplayed. While he is more forgiving than his brother Mario, he still acts rude from time to time.
- Catchphrase: In "Luigi Time!!!", he says "It is Luigi Time" whenever he's happy and "It is not Luigi Time" when things go wrong.
- Deadpan Snarker: He usually has something snarky to say.
- Gleeful and Grumpy Pairing: He's the bubbly Gleeful to his brother Mario's Grumpy.
- Jerk with a Heart of Gold: He's a nicer person than his brother Mario, but he often has moments of selfishness.
- My God, What Have I Done?: Twice in "Luigi Time!!!":
- In the Wii Photo Channel episode, he feels guilt over accidentally shooting his brother Mario, so he decides to relieve stress by playing more Wii.
- In the Paper Mario episode, when he realizes that the injuries he inflicted on Mario have put him in a paper coma, he realizes how selfish he's been and wishes for Mario's de-paperization operation to be successful.
- Series Mascot: He's basically the unofficial mascot of StacheBros, given that his mustache is used as the channel's logo and that he's the host of both "Luigi Time!!!" and "Luigi's New Year's Bash".
- Still Believes in Santa: Luigi is one of Santa's strongest believers, so much so that when Mario gets him to stop believing in Santa in "The Year Luigi Stopped Believing In Santa Claus!", Santa starts to fade out of existence and Christmas almost gets cancelled.
Princess Peach
- Damsel in Distress: As in canon, she constantly gets kidnapped by Bowser.
Toadsworth
- *Crack!* "Oh, My Back!": In "Toadsworth's Spontaneous Back Problems", his back constantly breaks to the point where he can't even stand up.
- Demonic Possession: In "The Curse of Toadsworth Mansion", he gets possessed by the spirit of Prince Peasley II, who plans to break his curse by assassinating the spirit of the King.
- Hidden Depths: Despite not actually being a doctor, he showed enough skill to transform Mario back to his normal self from his paper coma in the Paper Mario episode of "Luigi Time!!!".
- Scatterbrained Senior: He's old and sometimes behaves strangely.
Toad
- The Friend Nobody Likes: While Mario is the only one annoyed by Diddy, everyone is annoyed by Toad. Not even his own grandfather, Toadsworth, seems to care about him.
Princess Daisy
- Deadpan Snarker: She's the most snarky of the princesses.
Princess Rosalina and Luma
- Everyone Has Standards: In "Our Princess Is In Another Castle", she doesn't take kindly to finding out she's been kidnapped and lashes out at Peach for not doing more to prevent it from happening.
- Fish out of Water: Rosalina isn't fully accustomed to life in the Mushroom Kingdom due to living in space.
Donkey Kong
- Berserk Button: Stealing the Great Banana from him is a bad idea, as Goomba and Toadsworth find out the hard way in "Super Donkey Kong Bros".
- Dumb Muscle: He's strong but also one of the stupidest characters on the show.
Diddy Kong
- Butt-Monkey: Pun not intended, his suffering is usually caused by Mario's hatred for him.
Yoshi
- Big Eater: He wouldn't be a Yoshi if he didn't have a big appetite.
Antagonists
Bowser
- Abusive Parents: He treats his son more strictly than in canon. In fact, he almost threw his son into a pit in "Mario & Luigi! Stache Bros - The Stachey Sequel" for being unable to breathe fire, something the canon Bowser wouldn't do.
Bowser Jr.
- Inadequate Inheritor: In "Mario & Luigi! Stache Bros - The Stachey Sequel", his father views him as useless for being unable to breathe fire.
- Overlord Jr.: In "Mario & Luigi! Stache Bros - The Stachey Sequel", Bowser plans for him to be his heir once he learns about his existence.
Goomba
- Only Sane Man: He sometimes serves as the voice of reason among Bowser's minions.
Koopa
- Alternate Universe Reed Richards Is Awesome: In "Mario's Magical Mirror", the Koopa from the world within Bowser's magical mirror is one of King Toad's toughest minions.
- Hidden Depths: He proves to be a very fast runner in "Koopa The Quick Saves The Day?".
Boo
- Lady Looks Like a Dude: "Boo's Death Sentence" reveals that she used to be a regular Toad, but Goomba comments that she just looked like Toad with a bow.
- The Smurfette Principle: She's the only female member of Bowser's minions.
Petey Piranha
- Adaptational Intelligence: He seems to be somewhat smarter than his canon counterpart and he can even speak English, which he wasn't normally capable of doing in the games.
Spike
- A Lizard Named "Liz": He's a Spiny (a subspecies of Koopa that has spikes on its shell) named Spike.
- Never Learned to Read: He admits to being illiterate in "Spike in the Most Amazing Story Ever".
Chain Chomp
- Angry Guard Dog: Before being forced to work for Bowser, he served as one for the Mushroom Kingdom Penitentiary.
- Simpleton Voice: He's not very bright and has a throaty but goofy voice.
- Talking Animal: He's the Mushroom Kingdom's equivalent of an Angry Guard Dog and he has the ability to talk.
Kamek
- Token Wizard: He's currently the only member of Bowser's minions with the ability to cast magic spells.
- Training from Hell: His debut video, "Bowser's Minion Academy", has him putting Bowser's minions through rigorous training montages in the hopes of strengthening them. It only weakens them instead.
Wario
- Demonic Possession: In "The Curse of Toadsworth Mansion", he gets possessed by the spirit of the King.
- The Gambling Addict: In "Wario The Greedy", he gambles all of his money away at a casino in Canada, which leaves him desperate for cash.
- Perpetual Smiler: As a plush doll, he's designed to have a huge grin on his face.
- Would Hurt a Child: In "Home Alone", he threatens to subject Bowser Jr. to all the torture he put him and Waluigi through, and then some.
Waluigi
- Book Dumb: In "Home Alone", he admits to only having a preschool-level education.
- Forgotten Birthday: In "Mario & Luigi! Stache Bros - The Stachey Sequel", nobody seems to care about his birthday.
- Mistaken for Thief: After he and Wario have collected one billion dollars in "Wario's Robbed", he decides to deposit it all in a bank account after Wario explains the possibilities of having that much money. However, because he forgets to tell Wario what he planned to do with the money, Wario thinks his own partner robbed him blind.
- Would Hurt a Child: In "Home Alone", he plans on stabbing Bowser Jr.'s eyes with sharpened candy canes until he bleeds mint, which makes Wario concerned about his sanity.
