Shadow Mario
Shadow Mario is an evil doppelganger of Mario and the main villain of Super Mario Sunshine. He has the same appearance of Mario, except that his body is blue (with water effects) and his eyes are red. He also has an unusually long, red tongue. Shadow Mario wields the Magic Paintbrush, an invention created by Professor E. Gadd. Using the brush, Shadow Mario can created toxic goop and even some enemies. Ultimately, it is revealed that Shadow Mario was Bowser’s eighth child, Bowser Jr., in disguise. Using the Magic Paintbrush, Bowser Jr. could make him self look like Mario. It is unknown how Bowser Jr. acquired the paintbrush.
At the beginning of Super Mario Sunshine, Mario, Princess Peach and Toadsworth travel to the island resort of Isle Delfino to get some much needed R&R. However, when they arrive, they discover the island has been covered in toxic graffiti. Worse yet, Mario is arrested by the Pianta police. During his trial, Mario was found guilty of vandalizing the island, causing the Shine Sprites to lose their power. However, the real criminal was Shadow Mario. Since they looked so alike (at least to the Piantas), Mario was arrested instead of the doppelganger.
After being found guilty, Mario is ordered to clean up the graffiti. Until he does so, he is forbidden to leave the island. Shortly after being released, Shadow Mario appears and kidnaps Princess Peach. Mario chases him, shooting water from FLUDD, and rescues the Princess. However, Shadow Mario escapes before he can be caught. Eventually, when Mario is on another part of the island, Shadow Mario returns and kidnaps the princess a second time.
Shadow Mario takes Peach to Pinna Park. When Mario hears that the princess has been kidnapped, he immediately heads to the amusement park. Once there, Shadow Mario enters the cockpit of the gigantic Mecha Bowser, and begins to attack the plumber hero. After a long battle, Mario defeats the robotic creation. Then Shadow Mario opens the cockpit and reveals his true form, Bowser Jr. The young Koopa then reveals that his father, Bowser, told him that his mother was Peach and that she had been kidnapped by the “evil†Mario. Thus, Bowser Jr. decided to frame Mario to punish him and ultimately save his “motherâ€. That being said, Bowser Jr. activates his hot air balloon, and takes Princess Peach to Corona Mountain, where his father awaits his arrival.
Shadow Mario periodically returns to the island to cause trouble for the real Mario. In fact, Mario must battle Shadow Mario in every world of Isle Delfino, and fights him several times at Delfino Plaza. To defeat him, Mario must shoot water from FLUDD at an escaping Shadow Mario. Once defeated, Shadow Mario will give up a Shine Sprite, a Yoshi Egg, or a FLUDD nozzle.
In the end, Bowser Jr. loses the Magic Paintbrush, preventing him from assuming his identity as Shadow Mario. However, the runner Il Piantissimo discovers the brush on the sands of Gelato Beach. It is unknown what Il Piantissimo does with the paintbrush, or if he even gets it. Bowser Jr. is shown with it in other sports games, however these are in power shots, in the games where he is actually a boss like New Super Mario Bros., he is never even shown with it.
Shadow Mario is an unlockable character in Mario Golf: Toadstool Tour. Interestingly enough, Bowser Jr. is also a playable character. It is unknown if this Shadow Mario is an alternate version of Bowser Jr. or if it is someone else in disguise. This Shadow Mario may even be Il Piantissimo.