Tony Tony Chopper is a doctor and a blue-nosed reindeer. The power of the Zoan-type Human-Human Fruit provides him with the ability to transform into a full-sized reindeer or a reindeer-human hybrid. A self-developed drug he calls Rumble Ball enables him to perform even more transformations for three minutes. With help from Caesar Clown, Chopper can last in his transformations for about 30 minutes.
Rejected by his herd because of his blue nose and eating the Devil Fruit, Chopper is rescued by Drum Island’s quack doctor Doctor Hiriluk. While developing a potion to create cherry blossoms when in contact with snow, Chopper is heartbroken when Hiriluk falls ill with a deadly disease. After Hiriluk’s death, Doctor Kureha takes him in as his mentor. After the Straw Hats arrive at Drum Island and take Chopper with them, Kureha uses Hiriluk’s potion to turn the snowy sky into cherry blossoms, fulfilling Hiriluk’s life mission. When complimented, Chopper acts flustered and sometimes yells at the person who complimented him to stop trying to make him happy. A running gag within the series is when other characters mistake him as a Tanuki, and he angrily corrects them, pointing out that he is a Tonakai (Japanese for “Reindeer”).