Once you play a mini-game in Story Mode or Party Mode, it becomes unlocked. In Mini-Game Mode, to play Mini-Game Circuit, you have to have unlocked one four player game, one 2 vs. 2 game, one 1 vs. 3 game, and one duel game. In order to play Mini-Game Decathlon in Mini-Game Mode, you have to have unlocked Chomp Romp, Dinger Derby, Flower Shower, Ground Pound, Hydrostars, Later Skater, Leaf Leap, Night Light Fright, Triple Jump, and Will Flower.