The heart of "Mario Superstar Baseball" is the Challenge Mode. It is a single-player mode where the player selects a pre-built team and must defeat all the other teams; at first Bowser's team is the last team to beat for the cup, and must be unlocked before the player can use him. There are six teams, each led by one of the Captains (Mario, Peach, Yoshi, Donkey Kong, Wario, and Bowser), features a secondary captain (Luigi, Daisy, Birdo, Diddy Kong, Waluigi, and Bowser Jr.), and is filled with a mix of sub characters, some of which are duplicated within a team, but do not appear on any other team. For example, aside from the aforementioned captains and sub-captains, Mario's team consists of Monty Mole, 3 Piantas, and 3 Nokis, Princess Peach's team consists of Toadette, Toadsworth, and 5 Toads, Wario's team consists of Boo, King Boo, Petey Piranha, and 4 Magikoopas, Yoshi's team consists of Baby Mario, Baby Luigi, and 5 Shy Guys, Donkey Kong's team consists of Dixie Kong, Goomba, Paragoomba, 2 Paratroopas, and 2 Koopa Troopas, and Bowser's team consists of 4 Dry Bones, Hammer Bro, Fire Bro, and Boomerang Bro (although Hammer Bro, Fire Bro and Boomerang Bro are separate characters (enemies) in the Mario series, in this game, it is actually just a color variation of the same character.).