When he first appeared Coby was a small, timid, bespectacled boy with pink hair. He was slightly chubby and somewhat shorter than Luffy. After training with Garp, Coby became somewhat thinner and taller. He now stands nearly as tall as Luffy. He also gained a scar across his forehead above his right eye. He now wears a jacket with the standard Marine colors.
Coby is first introduced as a cowardly Chore Boy on board Alvida's ship. Through fear of being smashed by her Iron Mace, whenever she asked him who was the loveliest on the sea, he would reply, 'You are, Miss Alvida'. Eventually with the help of Luffy he found the courage to pursue his dream of leaving her and becoming a Marine.
The first time he appears to have changed is when he and Luffy arrive at the base Captain Morgan is at. Helmeppo holds a gun to his head, but he pulls together his courage and tells Luffy not to worry about him. After their mini-arc series, Helmeppo and he become good friends.
Coby values his friendship with Luffy a lot, as shown when even after their brief fight, he asks if they're still friends.
Abilities and Powers
In his first appearance he lacked any fighting skills. According to Alvida, the only reason why she kept him on was because he happened to be good at Navigation. He is seen during his mini-arc training alongside Helemeppo and Vice-Admiral Monkey D. Garp. He has since become strong enough to use Rokushiki, or at the very least, Soru. He also has some knowledge of swordsmanship, as he was seen practicing with Helmepppo, as well as Garp's attendant.
He appears to be at Water 7 alongside Helmeppo after Garp pays Luffy a visit. He tells both Luffy and Zoro about "The New World", and also tells them that the next time they met, it will be in the New World, and the he will be an Admiral and he will have to fight and capture Luffy. Luffy just says he'll look forward to their fight.
Coby sees Luffy one more time as he leaves Water 7, when Garp attacks.
Coby makes another appearance later on, in the Marineford Arc, participating in the war alongside the marines. After shouting a plea to end the war, he is attacked by Admiral Akainu, only to faint before being saved by Shanks.