A less common but still interesting trope is the 'swap universes' scenario. In this, the characters from Supernatural end up in The X - Files universe and vice versa. They have to navigate the different rules and cultures of the new world while still trying to find a way back home. It can lead to some really creative and humorous situations.
There are also a lot of 'Alternative Universe' (AU) fanfics. These can range from modern AUs where the characters are in a completely different setting, like high school or a corporate office, to fantasy AUs where they might be in a magical world. These AUs give writers the freedom to explore different aspects of the characters' personalities and relationships outside of the show's canon.
One common trope is the forbidden love between a human and a supernatural being, like a vampire. Another could be the power dynamics in sexual relationships within the supernatural world, such as an alpha werewolf and his mate. Also, the idea of soulmates in a supernatural context often features in these fanfics.
One popular theme is the relationship between Mulder and Scully. Fanfic often explores their unspoken feelings and how they deal with the strange cases in a more personal way. Another theme could be the expansion of the X - Files universe, like delving deeper into the conspiracy theories that are only hinted at in the show. And of course, there are fanfics that focus on individual characters' backstories, such as what made Mulder so obsessed with the paranormal in the first place.
One popular X Files shipper fanfic might be those that focus on the relationship between Mulder and Scully. For example, stories that explore their early days of partnership and the gradual development of their feelings. There are also fanfics that take a different turn in their relationship, like what if they got married earlier in the series' timeline.
One popular 'r x files fanfic' might be those that explore the relationship between Mulder and Scully in alternate universes. For example, there could be a story where they meet in a world where the X - Files never existed but they still have an immediate connection.
One popular trope is the 'fish - out - of - water' situation. For example, Mulder and Scully arriving in Twin Peaks and being completely bewildered by the town's strange customs and the odd characters. Another is the 'unlikely alliance' trope, where characters from the two shows who seem very different at first, like Agent Cooper and Mulder, team up to solve a mystery. There's also the 'hidden connection' trope, where it turns out that there are some long - forgotten or hidden links between the events in Twin Peaks and the alien conspiracy in The X - Files.
One common trope could be the 'enemies to friends to more' where they start off on opposing sides perhaps in a misunderstanding but gradually come to understand and care for each other deeply. Another might be the 'protective partner' trope, where Superboy is very protective of Robin due to his more fragile human form compared to his own Kryptonian strength. And then there's the 'discovering new powers together' trope, where they train and in the process, they learn new things about their abilities and how they can complement each other's powers.
Another trope is the 'damsel in distress' where the reader gets into some sort of trouble and Damon has to come to the rescue. But sometimes this trope can be flipped, and the reader ends up saving Damon instead, which is an interesting twist.
One popular trope is the 'stranger to lovers' trope. In many 'Link x Reader Fanfic', the reader character starts as a stranger to Link, and through their shared adventures and experiences in Hyrule, they fall in love. It's a classic and always makes for an interesting read.
Another trope is the 'power imbalance' trope. Graves, being an established and powerful wizard in MACUSA, and Credence, being a young and initially untrained wizard (or Obscurial). Fanfics might explore how this power difference affects their relationship, whether it's Graves using his power to protect Credence or Credence growing in power and challenging Graves in some way.