Shadow Mario an evil doppelgänger of Mario. He makes his first appearance in Super Mario Sunshine as Mario's enemy; Shadow Mario shares the shape of the plumber, but is completely blue - according to the game, he is made out of Graffiti. He uses his Magic Paintbrush to spread Graffiti and Goop across Isle Delfino, and dirties the Shine Sprites that keep the island sunny. He was seen causing havoc on Isle Delfino by some of its residents, causing them to believe that Mario was the cause of their troubles.
In all of the levels of Super Mario Sunshine, the player must chase Shadow Mario, squirting him with F.L.U.D.D.. It is eventually revealed that Shadow Mario is Bowser Jr., Bowser's son, and that the device he uses to vandalise the island was made by E. Gadd, F.L.U.D.D.'s creator.