Main characters
Mario
The hero and the character you control through most of the game. With his infamous jump attack and trusty hammer, he is ready to rise to the challenge.
Bowser
The King of the Koopas and Mario's ever-present nemesis. This time, he has stolen the Star Rod, which has made him all but invincible, and used it to lift Princess Peach's Castle high into the sky. Only with the help of the seven Star Spirits can he be defeated?
Princess Peach
Princess Peach has once again been kidnapped, this time, along with her entire castle! Every time Mario clears a chapter, Peach will play a short quest, assisted by the friendly star-in-training Twink, that often effects the game for Mario. She can choose what enemies and items he will encounter in Shy Guy's Toy Box, and send him items through a magical treasure chest located in the castle.
Twink
Twink is a newborn Star Kid who recently rose out of Starborn Valley, a few days before the story actually began, when Bowser took the Star Rod. He later comes to Peach's aid when she wishes for a way out, but he cannot fulfill her greatest wishes at that point. He is known to send messages to Mario on the next chapter, and give him some invaluable items. His greatest accomplishment is the defeat of Kammy Koopa, with some help from Peach.
Kammy Koopa
Kammy Koopa is Bowser's right-hand Koopa, who flies around on her broomstick and causes trouble for Mario and his companions throughout the game.
Companions
Goombario
Goombario is a goomba that knows a lot about the Mushroom Kingdom and all who inhabit it. You can use him outside of battle to tell you where you are, or what you need to do next. In battle he is able to tackle, or tattle on the enemy, revealing it's HP (hit points).
Kooper
Mario meets Kooper the Koopa after his shell was taken by the fuzzies. Once you return his shell he joins you. Kooper is able to launch his shell (with the help of Mario) to destroy obstacles, reach far away switches, or grab you something far away that Mario cannot reach.
Bombette
Bombette is a Bob-Omb trapped in the prison of the Koopa Bros. fortress, and with Mario's help, she frees herself and the other Bob-Ombs and joins Mario's party. She can use her exploding power to destroy cracked walls, as well as activating switches and stunning enemies in battle. Her primary attack is a body-slam, but by leveling up, she can acquire a variety of explosive atacks.
Parakarry
Parakarry is the Mushroom Kingdom's friendly mail Koopa. Once Mario Finds his missing letters, he will join the party and help Mario on his quest. He can fly Mario over short gaps, and dive-bomb enemies in battle. As you find letters laying around the Mushroom Kingdom, you can find the correct recipients and deliver them, often for rewards.
Bow
Bow is a Boo Princess who lives in Boo's Mansion, deep within Forever Forest. Her guardian is Bootler, the ghost of a butler. She holds a Star Spirit, Skolar, hostage in order to convince Mario to help her defeat the "Invincible" Tubba Blubba. The Boos have been terrorized by Tubba Blubba for quite a while, as Tubba's favourite meal are Boos. She agrees to go with Mario, against Bootler's will. Using her stealth skills, she helps Mario sneak into Tubba Blubba's Castle in Gusty Gulch. Upon Tubba's defeat, she gets Mario to let him accompany him for the remainder of the quest. She is very stubborn and loves getting things her way. Abilities including smacking enemies, with or without her precious fan, stealth, and scaring the heck out of enemies.
