Mario and Luigi are the main characters. They play important roles in the story.
The main characters include Mario and Luigi, who are on their adventure. Bowser, whose inside is the main setting. There are also some side characters like the Star Sprites. These little guys have their own unique abilities and sometimes help the main characters out. And of course, the various enemies that Mario and Luigi face can also be considered important characters in a way as they drive the action and challenges in the game.