Reginald could be a great addition. His leadership skills and his own motives could add an interesting dynamic to the story. Maybe he could be initially against Henry and Charles working together but then come around. Another good character is Ellie. Her combat skills and her loyalty could be useful in their adventures.
Well, perhaps they could be in a situation where they are framed for a crime they didn't commit. They then have to work together to clear their names. Charles could use his plane to escape from the authorities while Henry figures out who is behind the frame - up. They could also encounter some new characters during this adventure who either help or hinder them.
One popular Henry Stickmin fanfiction might be those that explore alternate endings to the game's scenarios. For example, stories where Henry makes different choices during the heist and how that changes the overall outcome. Another could be fanfictions that focus on the backstories of the characters in the Henry Stickmin universe, like Ellie's life before she met Henry.
One common theme is adventure. Since Henry Stickmin is often involved in heists and wild escapades, and Ellie Rose is his partner in crime in some scenarios, fanfics might revolve around their shared adventures.
First, get to know the characters really well. Play the Henry Stickmin games multiple times to understand their personalities, motives, and relationships. Then, think of an interesting concept. It could be something like a 'what if' scenario, for example, what if Henry had to complete a heist in a completely different setting like outer space. Next, start with a simple outline of the story, including the beginning, middle, and end.
Some dedicated gaming fanfic communities or forums could also be a good place to look. These places often have fans who are really into creating and sharing fanfics related to their favorite games, like Henry Stickmin. You might have to register and ask around to find the relevant fanfic.
There's no way to know just from 'Henry Henry novel' whether he is the protagonist. It could be that he is just a minor character or part of a sub - plot.
I'm not sure which specific 'Henry Henry' in a novel you are referring to. There could be many characters named Henry in various novels. Maybe it's a relatively unknown or self - published work. Without more context, it's difficult to determine who this 'Henry Henry' is.
I recommend "The Uncrowned King", a historical fiction novel. Although there was no mention of Charles IX and Prince Henry, the plot of this novel was very interesting. The protagonist brought the magical core to an ancient world similar to the early Ming Dynasty, gathered robots as helpers, recognized the emperor's father as a backer, practiced strange techniques, opened a medical center, developed science and technology, strengthened the country, and intimidated all countries. Finally, he became the uncrowned king. Cute robots, ancient technological development, and the historical background that was vividly portrayed would definitely make you unable to put it down. I hope you like this fairy's recommendation. Muah ~😗