Beast Boy could also be a mentor figure. He has a lot of experience with different forms of life from his own world. In the Pokemon fanfiction, he could teach young trainers how to respect and cooperate with Pokemon. He might share his knowledge about different animals which could be useful when training different types of Pokemon.
He might interact with Pokemon based on his animal forms. For instance, if he transforms into a bird, he could fly with flying - type Pokemon and learn their flight patterns. This would help him in battles as he could strategize better. He could also communicate with Pokemon that are similar to the animals he can transform into, using his understanding of their natural behaviors.
Maybe his dark secret could be related to his past trauma before he got his powers. For example, he might have witnessed something truly horrifying that made him the way he is.
Another reaction could be that he tries to hide his feelings by putting on a brave face. He might joke around even more to cover up the fact that he's really hurt. But deep down, his feelings are still damaged and this could lead to some bottled - up emotions that might explode later.
In a Marvel fanfic, Beast Boy could have a complex relationship with the Inhumans. His ability to change forms could be seen as both a threat and an asset. He might have to prove himself to them. Also, his connection to nature could be explored in relation to characters like Black Panther who also have a strong connection to a certain aspect of the world.
Maybe a girl with a similar power. For example, a girl who can communicate with animals telepathically. They would have a deep understanding of each other because of their shared connection to the animal world. They could go on adventures together, using their powers to help animals in trouble. Their relationship would be based on mutual respect for their powers and a shared passion for animals.
Well, the plot could involve Serena getting lost in a strange forest and stumbling upon a mysterious castle. Inside, she discovers a Pokemon that has been cursed to look like a beast. Serena, with her kind heart, tries to befriend the beast - Pokemon and through their interactions, they gradually break the curse. It could also have elements of Serena using her Pokemon battling skills to protect the castle from other threats while getting to know the beast better.
The plot could be that Serena is exploring a new region when she stumbles upon an old, abandoned castle. Inside, she finds a Pokemon that is trapped in a form that makes it look like a beast. This Pokemon was cursed long ago. Serena, being curious and kind, starts to interact with it. She brings beauty into its dark and lonely world. As they get to know each other, the Pokemon starts to change, becoming less beast - like. Their relationship evolves, and Serena has to face challenges from those who don't understand her connection with this strange Pokemon.
It might also explore how their different personalities interact in a relationship. Beast Boy is more laid - back and earthy, while Blackfire is ambitious and often power - hungry. Their love could be a journey of them finding common ground, like a shared love for adventure or a desire to protect the innocent in their own ways.
It could be Slade. Slade might manipulate situations to make Beast Boy look bad in front of his friends. He could spread false rumors or set up situations where Beast Boy fails, which would make Beast Boy angry at being wrongly accused and at the fact that his friends might start to doubt him.
One possible plot could be that a boy, who is a huge Pokemon fan, somehow gets zapped by a strange energy during a Pokemon event. He then slowly starts to transform into his favorite Pokemon, say Pikachu. As he turns into Pikachu, he discovers he can still think like a human but has all the powers of Pikachu. He then has to figure out how to reverse the transformation while also using his newfound powers to help other Pokemon in danger.