The Joker in fanfiction might target characters who are symbols of hope in Gotham. This could include some of the younger vigilantes or even ordinary citizens who have been shown to be brave. He could also target journalists who are trying to expose his crimes. Kidnapping them would not only be a way to stop the truth from getting out but also to create more fear in the city. And of course, any character who has a personal vendetta against the Joker and is not as powerful as Batman could easily be on his kidnapping list.
In this kind of fanfiction, characters like Barbara Gordon could be kidnapped. Since she has a connection to Batman and is also an important figure in Gotham. Another likely character is Alfred. The Joker might think that by kidnapping Alfred, he can really get under Batman's skin. Plus, any new sidekick or love interest of Batman's would be a prime target for the Joker's kidnapping sprees.
Batman's allies are very likely. For example, Robin. The Joker would see kidnapping Robin as a great way to taunt Batman. Also, Commissioner Gordon might be a target as he represents law and order, which the Joker loves to disrupt.
Maybe a family member of a police officer killed by the Joker. This civilian has a strong sense of justice and a personal vendetta. They are not bound by the same rules as the police and are more likely to take extreme measures. They have seen the destruction the Joker has caused to their family and will stop at nothing to get revenge.
Obviously, Harry Potter himself would be a main character. Since he's the son of the Joker in this fanfic. And Dumbledore would still likely be an important character, trying to guide Harry despite his new and strange heritage. Hermione and Ron would also be there, probably being confused and trying to help Harry deal with his new identity.
Another popular character could be Miyoshi. He has a certain charm and naivete in the original, and in fanfiction, this can be played with in various ways. For example, his growth as a character or his relationships with other characters can be explored more deeply, which makes him a favorite in the fanfiction world of 'Joker Game'.
I'd say Harley Quinn. She has a very unique relationship with the Joker. Her love for him, despite his insanity and abuse, adds a lot of depth to her character. And then there's Robin. His youth and idealism in the face of the Joker's evil present a great contrast. He represents the hope that Gotham can be saved from the likes of the Joker.
Batman is extremely common. Since the Joker and Batman have such a long - established relationship in the original comics, it's natural to see them cross over in fanfics. Their eternal battle of wits and the Joker's attempts to outwit Batman in new and different universes make for great reading.
Well, often there is the theme of chaos. The Joker is all about chaos, so in the fanfiction, his kidnapping might lead to total mayhem in the city or among the other characters. There could also be a theme of the kidnapped character's transformation, either becoming stronger in the face of the Joker's madness or losing their sanity as well.
Harley Quinn is quite interesting. She's caught in the middle between her love for the Joker and her own sense of self. Commissioner Gordon is also important. He's the one who often has to deal with the aftermath of Batman and the Joker's battles and is a symbol of the law in Gotham.
Obviously, Batman and the Joker are the most popular. Batman is the hero, with his cool gadgets and detective skills. The Joker is the chaotic villain, always coming up with wild and unpredictable plans. Robin also often appears in fanfiction, as Batman's sidekick. He adds a bit of youthful energy and sometimes gets into his own mini - adventures while helping Batman.
Well, I think Scarecrow would be an interesting character to pair with the Joker. They both have a knack for spreading fear in Gotham, and their combined efforts could be truly terrifying. Additionally, Poison Ivy could be paired with the Joker. She has her own motives and methods, and when combined with the Joker's madness, it could lead to some unique and unpredictable stories. And of course, Commissioner Gordon. His no - nonsense attitude against the Joker's chaos would make for a great dynamic in fanfiction.
Batman would definitely be a main character. He's the Joker's arch - nemesis, and when the Joker becomes a baby, Batman might be the one who first discovers him. He'd be in a moral dilemma about what to do with this baby version of his greatest enemy.