To create a believable character arc for Killer Croc, start with his backstory. Show his early life and how he became the way he is. Maybe he was once an ordinary person who was experimented on. Then, as the story progresses, have him face challenges that force him to change. For example, if he meets a group that accepts him, he might start to become more trusting. By the end, he could be on his way to becoming a more heroic figure, or at least less of a feared outcast.
Killer Croc was born Waylon Jones with a rare skin condition that made him look reptilian. He was bullied and ostracized, leading him to a life of crime.
His origin story is also a common theme. Writers might expand on it, change certain elements, or explore how his past traumas have shaped him into the character he is. For example, they could delve deeper into his genetic mutation and how it affected his life growing up, his family's reaction, and how that led to his life of crime in Gotham.
In Batman fanfiction involving Killer Croc, their relationship is often complex. Killer Croc is a formidable foe for Batman. He represents a more bestial and primal threat compared to some of Batman's other villains. Their encounters can be really intense. Batman has to use his wits and combat skills to deal with Croc's brute strength. Fanfiction might explore how Batman tries to rehabilitate Croc at times or just keep him in check in Gotham's sewers where Croc often lurks.
There are fanfictions that explore their relationship in different ways. Maybe in one, Baby Doll uses her charm and wits to get Killer Croc to see a different side of life. It could involve her helping him to overcome some of his more violent tendencies while he protects her from other threats in their world.
One possible plotline could be that the Killer Croc is accidentally transported to the Forbidden Forest in Hogwarts. The Hogwarts professors and students then have to figure out how to deal with this dangerous and unfamiliar creature. Another plotline might involve a dark wizard using the Killer Croc as a weapon to attack Hogwarts, and the students have to find a way to stop it.
In Batman Killer Croc fanfiction, there could be an unusual alliance where Killer Croc teams up with Batman against a common enemy. This enemy could be a new supervillain who has a plan to take over Gotham's underworld and Croc's territory. Croc might see the benefit of working with Batman temporarily to protect his own interests.
One plot idea could be that Killer Croc somehow ends up in the Naruto world and has to learn chakra control. Maybe he starts as a villain but then teams up with Naruto's group against a greater threat.
Their different personalities also play a part. Killer Croc is often associated with brute force, and Baby Doll with her charm and manipulation. When combined in a fanfiction, it can lead to unique plotlines where they balance each other out or clash in unexpected ways. They both also have their own complex backstories which can be explored further in a fan - created story.
One plot idea could be Killer Croc forming an unlikely alliance with a small group of outcasts in the city. They initially fear him because of his appearance but come to realize he has a good heart. Another could be Killer Croc's struggle to adapt to a new environment outside of his usual sewers, perhaps in a more rural area where he has to deal with different challenges. A third idea is a story where Killer Croc discovers a hidden power within himself during a fight with a powerful enemy and has to learn to control it.