One interesting aspect is the exploration of different character arcs. In PMMM fanfic, authors often delve deeper into the backstories and emotional growth of the magical girls. For example, they might expand on Sayaka's struggle with her ideals and how it could have turned out differently. Another aspect is the alternate universes created. Fanfic writers can imagine a world where the rules of the Puella Magi system are altered, leading to unique and unexpected storylines. Also, the relationships between characters can be explored in new ways, such as the friendship between Madoka and Homura being tested in unforeseen circumstances.
One good PMMM fanfic is 'A Different Ending'. It offers an alternative conclusion to the story that is less tragic and more hopeful. Another one is 'The Power Within' which focuses on the development of the magical girls' powers in a more detailed way. There's also 'Friendship Beyond Time' that explores the deep bond between the characters across different timelines.
One idea could be a crossover with Sailor Moon. The magical girls from PMMM could meet the Sailor Scouts and learn different ways of using magic. They might also compare their struggles against evil, like how the PMMM girls face witches while the Sailor Scouts battle the Dark Kingdom.
In Madoka x Homura fanfiction, the power dynamics between them can be an interesting aspect. Madoka, as a very powerful magical girl, and Homura, with her time - looping abilities, have a unique relationship. Fanfiction could play with how they use their powers in relation to each other. Maybe in a fan - created scenario, they combine their powers to save a new threat that wasn't in the original series.
One popular trope is the 'time - loop fix - it' where Homura uses her time - looping abilities to try and create a perfect situation for Madoka. This often involves Homura going through multiple loops, each time learning more about Madoka and how to protect her better.
Another theme is time - related. Since Homura has the ability to manipulate time in the show, many fanfictions play with this concept in relation to her relationship with Madoka. For example, stories might involve Homura going back in time to save Madoka in different ways or dealing with the consequences of her time - traveling on their relationship.
First, decide which two universes you want to cross over. Then, research both. For example, if it's a PMMM and Naruto crossover, study the characters, powers, and rules of both worlds. After that, come up with a basic plot like the PMMM girls getting lost in the Naruto world and having to find their way back while dealing with ninja battles.
One great pmmm male oc fanfic could be about a male OC who has unique magical powers and gets involved in the complex world of Puella Magi Madoka Magica. He might start as an outsider but gradually becomes an important part of the story, forging alliances with the magical girls and facing off against the witches.