If you're reading my comic you already know about Ash, Misty, Brock, Jesse, James, and Meowth. I have chosen not to answer any of the questions surrounding them ('Who is Ash's dad?' 'Is Brock Black?' and the like) but I do bring their personalities out a bit more than the show allows. Here's how I write them:
Ash: Ash and Pikachu are written slightly less annoying than on the show. Ash often carries Pikachu around as if it were really a pet and not some bizarre furry kid that he talks to.
Misty: I won't lie; I dislike Misty. I find her to be self-centered, caring more about Togepi than the humans around her. She spends most of her time on the sidelines, making sarcastic comments about Ash when he can clearly hear her.
Brock: Brock's value as the den mother of his group is emphasized, as we'll be seeing him cooking and even expressing concern for Team Rocket when they don't appear to ruin things. He knows hardship and how to overcome it, and will extend a helping hand to nearly anyone. In the predominantly caucasian Hamarkia, he often gets mistaken for black.
Jesse: Jesse often uses her impoverished background as an excuse for her chosen career in life, despite the fact that others have gone through worse and made it out okay (ie Brock. Have you noticed that Jesse's the only girl he hasn't had interest in?). She can easily hold her own in a hands-on fight, beating actual Pokemon in strength and swinging a chain as a deadly weapon...while riding a unicycle.
James: Because he's so fun to write, and a fan community favorite, he gets more spotlight than the other canon cast. Despite being chased across the country by Charlie and Angel, he manages to extend a friendly hand to Charlie. He has a multitude of unusual talents due to his upbringing with many tutors and private schooling. He gets his many roses from a small rosebush in a window box that hangs from the balloon. He's sweet, childish, and remarkably idiotic. It'll be fun.
Meowth: Have you ever noticed how Meowth has an Archie Bunker accent? I emphasize the similarity by making him a world-weary jerk. He sometimes has some camaraderie with Jesse, for both of them are unsatisfied with their station in life, but treats James as though he were retarded. He does have some joy in life; he likes to cook. It's too bad Team Rocket can't afford food.