Well, it depends on your taste. Some 'Penguin x Riddler fanfiction' might focus on their criminal partnerships in Gotham. They could be plotting together against Batman or other villains. You can explore different platforms to find the ones that suit you best.
A lot of 'Penguin x Riddler fanfiction' has the theme of power struggle. Since they are both strong - willed villains, they could be vying for control in Gotham's criminal hierarchy. And sometimes, there's a theme of unexpected friendship or partnership that develops between them in the face of common enemies.
Penguin and Riddler are typically not friends. They often operate independently and may even compete or have conflicts with each other in the comic universe.
The contrast between their characters. The Penguin is more of a brute - force type, while the Riddler is all about his intellect. Their interactions can be really engaging as they try to outmaneuver each other or work together.
One popular 'Penguin x Riddler' fanfic is 'The Unlikely Alliance'. It delves into how the two villains, with their distinct personalities, form a partnership that no one expected. They start off distrusting each other but as the story progresses, they realize they can achieve more together in Gotham's underworld.
One great 'Batman x Riddler Fanfiction' is 'The Riddler's Redemption'. It shows an interesting take on the Riddler trying to turn over a new leaf and his complex relationship with Batman during that process.
You can start by looking on Archive of Our Own (AO3). It has a large collection of fanfictions, and there are quite a few 'Batman x Riddler' ones. Just use the search function and type in the relevant tags.
One great 'Riddler x Reader' fanfiction is 'The Riddler's Enigma'. It delves deep into the complex relationship between the Riddler and the reader. The story is filled with his signature riddles and the reader's attempts to understand him. Another good one is 'Unraveling the Riddler'. It shows a more vulnerable side of the Riddler, which makes for a very interesting read when combined with the relationship aspect. There's also 'Riddler's Redemption in Love' which takes the character on a journey of self - discovery while falling for the reader.
A good 'the riddler x reader fanfiction' often has a strong portrayal of the Riddler's character. His intelligence and his love for riddles should be well - represented. Also, the relationship between the Riddler and the reader should be developed in an interesting way. It could start with a sense of mystery or danger.