One great 'Joker x Rachel fanfic' could be 'The Unlikely Bond'. It delves into a scenario where Joker and Rachel have a series of unexpected encounters that make them re - evaluate their views of each other. Another could be 'Joker's Redemption through Rachel' which shows how Rachel's goodness might start to change the Joker in some ways. There's also 'Rachel's Dilemma with the Joker' which focuses on Rachel's internal struggle when dealing with the Joker.
You can try Archive of Our Own (AO3). It has a large collection of fanfics from various fandoms, including ones related to the Joker and Rachel. Another option is Fanfiction.net. It has been around for a long time and has a decent amount of 'Joker x Rachel' fanfics.
In Harley Quinn x Joker fanfic, the character development is often a focus. Harley's transformation from a psychiatrist to a criminal sidekick is interesting. Writers may play with different timelines and scenarios in the fanfic. For example, they might explore what would happen if Harley finally broke free from the Joker's influence earlier than in the original story. This can lead to various plot twists and new character arcs for both Harley and the Joker.
One common theme is the exploration of their different worlds. Percy from the demigod world and Rachel from the mortal world. Fanfics often deal with how they bridge this gap.
One common theme is friendship. Many fanfics explore how Ira and Rachel start as friends and how that friendship might develop into something more. Another theme is growth. They both grow as individuals within the relationship, learning from each other. For example, in some fanfics, Ira might learn to be more open because of Rachel, and Rachel might become more confident because of Ira.
One common theme is the clash of good and evil. Robin represents justice and order, while the Joker is chaos incarnate. Another theme is the psychological battle. They often try to outwit each other mentally.
Well, in 'joker x batman fanfic', the theme of duality is quite prominent. Batman and the Joker are two sides of the same coin. They both exist in the dark world of Gotham, but they have completely different approaches. Also, the theme of redemption sometimes creeps in, especially in fanfics where the Joker might be on the verge of a change or Batman is trying to find a way to save his enemy from himself. And of course, the theme of the cat - and - mouse game, which is always exciting to read about.
One common theme is the development of their relationship. It often shows how they start from being just friends or comrades in the game's world and gradually grow closer romantically.
Redemption can also be a theme. Maybe Joker is on a path to change through his interactions with Sae, or vice versa. It gives a sense of growth to the characters within the fanfic world.
For a Palutena x Joker fanfic to be good, it needs to explore the contrasts between them. Palutena is a goddess with a more traditional and divine presence, while Joker is a modern - day teenager with a dark and edgy side. The fanfic could use these differences to create interesting dialogues and situations. For example, when they first meet, Palutena might be confused by Joker's strange clothes and weapons, while Joker could be in awe of Palutena's beauty and power. Also, a good fanfic would have a proper pacing, not rushing through their relationship development but also not dragging it out too long.