Bowser Jr. first appeared in Super Mario Sunshine and disguised himself as Shadow Mario in Super Mario Sunshine and spread toxic goop across Delfino Isle. He was tricked by Bowser into thinking that Peach was his mother and that Mario and Bowser had reversed roles. Unaware of this, Mario, Princess Peach and Toadsworth headed to the island for a vacation and Mario was taken in by the police. Being framed by Bowser Jr., Mario and F.L.U.D.D. had to clear the waste from the island and uncover who truly caused this mess, when it was later revealed to be Bowser Jr. and Bowser.