Coby is a weakling at the beginning of the story who wants to become a marine but doesn't have the courage to do so. He starts the story off as a cabin boy on the pirate Alvida's ship and is too scared to try and leave until he meets Luffy. Through the time he spends with Luffy in the first volume he grows a lot and goes from a super anxious and scared kid to someone who is determined to follow his dream no matter what.

Coby changes significantly later on in the series and becomes a very strong and dependable marine. There is a chance that we may have to recast him later on if the VA cast isn't able to do both his weaker voice and when he becomes stronger because they are quite different. If you are able to do both voices though feel free to do a take of a line or two with his future voice as well, since we would like to be able to keep the same person throughout.

Voice Reference: https://www.youtube.com/watch?v=qvNqmsJdc2U