Explore his relationships more deeply. Maybe he has a soft spot for a certain character, like a little mouse that he secretly protects. This would add layers to his character. Also, show his internal struggle between his evil side that wants to cause trouble for Courage and a side that might be tired of being the bad guy all the time.
Well, one special thing could be its unique art style. The illustrations in Katz graphic novel might have a distinct way of depicting characters and settings, making it visually appealing.
It's possible that they have an adventure related to a school project gone wrong. For example, if they are doing a project on Greek mythology and accidentally summon a minor deity or a mythical creature. Then they have to figure out how to send it back without causing chaos in the school and also keep it a secret from the regular students.
Goode's underhanded words meant that some people or organizations looked normal on the surface, but in fact, they had ulterior motives and actions. This kind of behavior often used deception, false propaganda, illegal acts, and other means to achieve their unspeakable goals.
The main plot likely involves the relationship between the boy and Mr Katz. It could be about their adventures, how they interact, and what they learn from each other.
The boy is one of the main characters. He is probably the one through whose perspective we see the story unfold. And Mr Katz, who must be an important figure in the boy's life in the context of this story.
There's not enough information to really know who Jeff is. He could be anyone - a fictional character, a real person the storyteller knows, or even the storyteller themselves.