Luigi receives a letter informing him he has won a mansion as the grand prize in a contest. Luigi is puzzled; he never entered a contest. When he arrives at his mansion, he discovers that it is haunted with ghosts and Mario trapped inside.
Mario and Peach go on a vacation to Isle Delfino. But their trip soon gets spoiled after an imposter disguised as Mario paints and pollutes the entire island. Mario must clear his name, and clean up the entire island.
Mario and friends once again jump into the seat of their go-kart machines for the Wii installment of the venerable franchise. Now featuring an online racing mode, new motorbike vehicle types, and a special balancing system.