Tin Banana Tu
From the Super Mario Wiki
A Tin Banana Tu is a foul-tasting, purple-colored type of banana found on Kongo Bongo Island. It appears in the Donkey Kong Country television series during the episode "Speak No Evil, Dude". The Tin Banana Tu proves to be vital to the survival of the residents of Kongo Bongo, as it is needed for Cranky Kong's Kongo Bongo Gone Wrongo disease vaccine.
During the events of Speak No Evil, Dude, Cranky Kong is seen with several of these bananas, using them to make his vaccine. Later in the episode, Diddy Kong is given the fatal Kongo Bongo Gone Wrongo disease, so Donkey Kong heads out to find a Tin Banana Tu on the far side of the White Mountains, where a plantation for Tin Banana Tu bananas exists. Before the uncommon banana is given to Diddy, it is stolen by Polly Roger (disease's carrier), who then attempts to give it to King K. Rool, another victim of the disease, for a safe full of crackers. However, the banana soon falls into the hands of Donkey Kong, who allows King K. Rool to be cured by the purple banana in order save the island after realizing that another remedy was available for his best friend within a coconut.