AppearanceMost of the time, Chopper is a toddler-sized human/reindeer hybrid, his devil fruit abilities allow him to change his appearance depending on the situation. Chopper's left antler has a metal plate wrapped around it at all times, from being broken in a fight when he was younger. The usual clothing he wears include a pink, fuzzy top hat with a sideways medical cross (given to him by Hiluluk) and a purple pair of shorts. Chopper also has a remarkable feature that no other reindeer have, and that is a blue nose, while normal reindeers have black ones. As Oda's style evolved, Chopper has been given a more "chibi" appearance. This means that when in his Brain Point, Chopper has a larger head and eyes.
A running gag is that various characters in One Piece think Chopper is a tanuki (raccoon-dog, often simply translated as "raccoon") whilst in his Brain Point form. This is a play on the similar word "tonakai," the Japanese word for reindeer, from which the "Tony" in Chopper's name is derived. His heavy point form likewise is mistaken for a gorilla or an abominable snowman.
Lots of female characters find Chopper very cute such as Porche .
Oda has stated that he uses the color pink to represent Chopper, and (Oda was answering the questions as Chopper) for his smell, "how am I supposed to know?".
PersonalityChopper is naive and highly timid, often acting like a child because he doesn't know any better. In particular he is a coward at times like Usopp and Nami, his cowardice is mostly due to his childishness and overall lack of trust in his own fighting skills against the bigger foes (a contrast to Nami's self-survival based cowardice and Usopp's fear based cowardice). Chopper is more or less on a journey to define himself, seeing almost anyone on his team as a role model and in some cases, imitate their behavior, especially Usopp. He is an upright friend and companion who will try anything to overcome a task given by his team. He still has a feeling of distrust for humans for his youth and will often outright insult and claim that compliments don't make him happy to a human who compliments him while obviously being happy about it (he starts to smile and also dances a little). Chopper seems to be very forgiving of those close to him, for when Usopp wanted to rejoin the crew at the end of the CP9 arc, he called out to Luffy and Zoro, although they were ignoring him completely. As a running gag, Chopper will often believe almost anything he is told, and easily becomes victim to Usopp's lies. For some odd reason, he also believed Nami after she lied that she was a man, even after the truth was obvious.
When Chopper recognizes someone needs medical attention he often will start to panic and scream for a doctor, just to realize that he is one. He would rather run and hide than fight, but becomes more courageous when others are there to support him. He also has very high regards for his own profession of doctor. His dream is to become a doctor that can cure any illness, and he most respected Dr. Hogback for the huge amount of people he had saved. When Hogback informed him of his work with zombies in order to revive the deceased, Chopper still held him in very high esteem, believing that healing the hearts of those touched by tragedy was the highest possible calling for a doctor. When he discovered that Hogback wasn't actually reviving the dead, but merely using their bodies as puppets, Chopper became furious and refused to acknowledge Hogback as a doctor.
Another one of Chopper's habits is his reverse cartoon peek, where he stands behind a wall or a doorway and peeks at people, trying not to be seen by them. Unfortunately he's not hiding his body behind the wall, as a result his body is visible and only one half of his face is hidden.
n the group, Chopper often fools around with Usopp and Luffy for laughs and is also a thankful listener to Usopp's lies, most of which he really believes, at least for a short time. Normally Chopper is one of the first to join in with Luffy's antics, as well as watching in glee for some of Usopp's stunts. Robin calls him "Doctor-San" which makes him dance in joy. Sanji originally wanted to cook Chopper and jokingly wants him to join as "emergency food supply". Throughout the series, Sanji continues to refer to him as "the emergency food supply" to tease him but considers him a friend. Chopper also seems to have a close relationship with Zoro, who he often runs to when he's scared, and it is seen that Zoro is the one to save him when he comically falls into any form of water when trying to escape Nami's wild mood swings. Chopper originally wasn't hired to be the ship's doctor by Luffy, but just for being a "cool reindeer that can transform". The other boys of the crew have often mentored Chopper on what it means to be a real man; He is the youngest crewman, not originally human, and has had a relatively sheltered life.
FriendsBack on Drum Island, the people have come to accept his help in defeating Wapol, even though originally they were afraid of him. Chopper has also gained Dalton's respect.
EnemiesOne of Chopper's major enemies is Wapol, the spoiled king who insulted the death of Chopper's surrogate father, Dr. Hiluluk, among other things. Chopper initially idolized Dr. Hogback, but after learning of his disregard for human life and coming into conflict with him and the rest of Gecko Moria's forces, he declared that he no longer considers him a doctor. He is wanted by the Marines, albeit with an extremely low bounty of only fifty Beli.
The HerdChopper's real family is a herd of Reindeer, who abandoned him for being different. Initially estranged for being born with his blue nose, he is further abandoned after eating the Hito Hito no Mi, which gives him an "unreindeer-like" humanoid form. He eventually found his paths intertwined with them during his days with Hiriluk and was beaten up. However he was able to pass through them despite this and achieve his goal at the time.
HirilukHiriluk was Chopper's mentor who took him in and became his "father". They had a close relationship with each other, and had formed a deep bond despite their almost constant arguing with each other. Despite his time spent with the superior Doctor Kureha, Chopper refers to Hiriluk as "the greatest doctor in the world." Hiriluk also gave Chopper his name, claiming his antlers looked like they could chop down trees.
KurehaThough neither family nor claiming to have adopted him, Doctor Kureha is his mentor. While she often hides her feelings towards him she considers him like a "son" to her. She is happy to know he is currently well.
Abilities and PowersBasic Transformations: As previously mentioned, Chopper ate the "Human-Human Fruit". This is a "Zoan"-type fruit which gives the one who eats it three basic transformations:
* Walk Point: This is Chopper's true form, useful for general travel on foot. It is also in this form where his olfactory senses are at their highest. As a result, Chopper often make use of his default form for tracking purposes, though certain scents seem to dull his sense of smell. Chopper's reindeer appearance often comes in handy, as enemies will usually assume he is just a harmless pet when they haven't heard him speak. This was especially useful in Arabasta, when he played an instrumental role in Sanji breaking the others out of Rain Dinners. Called "Sprint Boost" in the English dub and "Limb Boost" in the English manga.
* Brain Point: With a small body and large head, this form is how Chopper is generally characterized in media. Different from humans who eat Zoan-type Devil Fruits, Chopper generally doesn't remain in his real form, and this can be explicated due to the advantages of having free arms, also needed for using his medical abilities. He is smarter in this form, and also inexplicably cute. In addition he can scope out an enemies weakness in this form while he is under the influence of a Rumble Ball. This is also the form where he does his best thinking because he can utilize both human intelligence and reindeer sensitivity at the same time. In the English version, Brain Point is called "Brain Boost".
* Heavy Point: Chopper's "human" form, which gives him the form of a tall, muscular ape-man. He uses this form to help steer the ship. This form imbues Chopper with super-human strength. In fact, when he first used this form against Luffy and Sanji (who were trying to catch him and eat him) Chopper was able to knock both Straw Hats out at the same time. In the 4Kids dub this form is called "Heavy Boost", and his voice becomes deeper, while in the Viz Manga and FUNimation dub it's called "Weight Boost" and his voice stays the same (such as in the Japanese version).
Rumble Ball Transformations: Additionally, Chopper has added on to these by use of the "Rumble Ball", which gives its user several more transformations for three minutes by 'distorting the wavelengths of transformation':
* Jumping Point: Chopper keeps his reindeer legs in a human-like form, which allows him to jump long distances. "Jumping Boost" in the English version.
* Arm Point: Chopper's second most powerful form, his fore-hooves become extremely muscular in his human-esque form, allowing him to deliver devastating punches with his front hooves. In the English version, this is called "Arm Boost."
* Horn Point: Similar to Walk Point, but Chopper's forelegs get bulkier and his antlers become larger and sharp. In addition, Chopper has human fingers in this form. In the English version it is called "Horn Boost".
* Guard Point: Chopper's fur grows out and becomes an impenetrable shield against outside attacks. He looks like an overgrown Chia Pet in this form. In the English version it is named "Guard Boost".
It has recently been revealed that Chopper can't eat multiple Rumble Balls back to back within 6 hours or otherwise he'll lose control of his transformations.
Monster: It seems that the consumption of three Rumble Balls in under six hours created a new Point in which he is standing similar to Heavy Point, but possesses an oddly misshapen head and antlers, as well as an incredible (likely more than twenty feet, or about the size of an office building) increase in height and strength. Chopper's fur is lengthened in this form. Chopper also loses all consciousness and goes completely berserk in this form. Also, this form appears to be a combination of all of Chopper's transformations, not including Brain Point and Arm Point (Heavy Point stance, Walk Point speed, Horn Point horns, Jump Point legs, and Guard Point hair). Doctor Kureha told Chopper that after he consumed three Rumble Balls for the first time, he leveled an entire village on Drum Island while in this form. Kureha also commented on this form being that of a true monster; a danger to friend, foe, and even Chopper himself. According to Zoro's observation, this transformation appears to be lethal to Chopper, as the amount of energy needed to maintain the form is too much for his little body to handle. The only known way to end this form is by placing Chopper into the sea.
Chopper being the doctor of the crew, has a large knowledge of medicine and medical drugs as well as the preparation of remedies and ointments from regular fruits, roots and vegetables found on most islands. Most of this he learned during his apprenticeship under Dr. Hiruluk and Dr. Kureha. In addition to the transformational advantages that Chopper's Zoan forms afford him in battle, he has also been known to employ wrestling-type moves (i.e.pinning down an opponent,or smashing them to the ground by means of a suplex) from time to time. His extensive knowledge of the bipedal anatomy also proved useful when the Straw Hats were trying to bring down Oars, during which time, Chopper formulated several theories on where it was best to target the colossal adversary. And while naive, he can be quite a capable strategist, as seen on his fights against the Mr. 4 pair and Gedatsu.
Chopper, who originally was an animal, is also capable of speaking to and understanding other animals, which has come in handy during points in the story.
Chopper also seems to have a technique called Tranquilizer (sometimes translated as Sedative, as is the case with the English manga), which involves Chopper injecting a substance into the opponent making them faint. This was first used on Luffy when he had a hallucination of a tsunami about to hit them while walking to Yuba in the Arabasta Desert.