Tony Tony Chopper is a reindeer from Drum Island who ate the Hito Hito no Mi, a Devil Fruit that granted him human intelligence and the ability to transform between different forms. Because of this, he was cast out by both humans who saw him as a monster and other reindeer who considered him a freak. He wandered alone until a kind-hearted but incompetent doctor named Dr. Hiluluk took him in and gave him a home, a purpose, and a father figure for the first time in his life.

Hiluluk dreamed of curing all sickness in the world and passed that dream on to Chopper before tragically sacrificing his own life. Devastated by the loss, Chopper was then taken in by Dr. Kureha, a brilliantly skilled doctor who trained him in real medicine and helped him master his Devil Fruit transformations through the use of a drug called the Rumble Ball. Under her harsh but caring guidance, Chopper grew into a genuinely talented doctor capable of treating almost any condition.

When Luffy and the Straw Hat Pirates arrived on Drum Island, Chopper was initially suspicious and kept his distance. But Luffy’s unconditional acceptance of him, monster form and all, broke through his walls completely. Chopper joined the crew with the dream of one day becoming a doctor who could cure any disease in the world, carrying forward the legacy of both Hiluluk and Kureha with every patient he treats.