Tony Tony Chopper (トニートニー・チョッパー Tonī Tonī Choppā), nicknamed "Cotton Candy Lover" Chopper (わたあめ大好きのチョッパー Wata-ame Daisuki no Choppā), is a doctor and a blue-nosed reindeer who gained human properties by eating the zoan-type Human-Human Fruit (ヒトヒトの実 Hito Hito no Mi), granting him the ability allows him to change between three forms. His first and original form is that of a reindeer. In his second form, he has the proportions of a human child, while retaining his antlers, hooves, and fur. In his third form, he looks like a brawny man with fur or a gorilla. In addition to his normal transformations, Chopper developed a drug he calls Rumble Ball (ランブル・ボール Ranburu Bōru), which allows him to assume four additional forms for the duration of three minutes. These forms focus on certain aspects of his body to improve his physical abilities. These are broken down into six "points" in the original version called: guard, horn, jumping, and arm point with the original three becoming walk, brain, and heavy point. If Chopper uses a second Rumble Ball within six hours, he cannot control his transformations. If he uses a third Rumble Ball within six hours of the first, he transforms into a monstrous version of himself and loses all self-control called "Monster Point". After the time-skip Chopper only needs to take a rumble ball for one point which is yet unknown. He is not capable of hiding his feelings. Chopper is voiced by Ikue Ōtani in the Japanese version of the anime; Kazue Ikura acted as a substitute for episodes 254 through 263. In the English version of the series, he is voiced by Lisa Ortiz in the 4Kids dub and by Brina Palencia in the Funimation dub.

When creating Chopper, Oda stated that he wanted a mascot who is both cute and fearless. An IGN review of the manga praised Chopper's character as one of the best in the series and said that he was able to be both touching and funny. Chopper ranked in the Top 5 of both Shōnen Jump character popularity polls since the character's introduction.[1] Oda said that the message he wanted to illustrate in regards to Chopper's family situation is that a person who is not blood-related to another person can still be considered as a member of one's family.