Another great concept is a crossover where Eleven's powers are mistaken for some kind of witchcraft by the Supernatural universe. Sam and Dean initially think she's a threat but then realize she's actually a powerful ally against a common enemy. They could be facing a powerful being that can manipulate time and space, and Eleven's telekinetic and telepathic abilities are crucial in defeating it.
One great Stranger Things crossover fanfiction is the one that combines it with 'Harry Potter'. It imagines the characters from Stranger Things attending Hogwarts. The way the Upside Down is incorporated into the magical world is really interesting. It adds a new layer of mystery and danger.
In a world where Hawkins and the kaiju realm collide, Godzilla emerges in the Upside Down. Eleven senses his presence and is both terrified and intrigued. The Demogorgons try to attack Godzilla, but his atomic breath incinerates them. Meanwhile, the kids of Hawkins are in awe as they watch this giant creature fight their otherworldly enemies. Godzilla becomes an unexpected ally in their fight against the darkness of the Upside Down.
To write a good Stranger Things crossover fanfiction, you should also focus on the relationships between the characters. How would Eleven interact with Luke Skywalker? What kind of friendship would form between Dustin and a character from 'The X - Files'? Building these relationships can make the crossover feel more natural and engaging for the readers.
One idea could be that the Demogorgon from Stranger Things somehow ends up in Derry from It. The Losers' Club and the kids from Hawkins could team up to fight it. They would have to combine their different skills and knowledge of the supernatural.
One idea could be that the Losers' Club from 'It' somehow ends up in Hawkins, Indiana, during the events of 'Stranger Things'. They could team up with the kids from 'Stranger Things' to fight a new, combined threat that has elements of both the Upside Down monsters and Pennywise's terrors. For example, the Mind Flayer could merge with Pennywise in some way, creating an even more terrifying entity.
A Stranger Things and Avengers crossover fanfiction could be filled with lots of interesting storylines. The Upside Down could be a new threat that the Avengers have to face. Steve Rogers could lead the Hawkins kids, teaching them about strategy and combat. Meanwhile, characters like Thor could be intrigued by the strange creatures from the Upside Down. The different powers and personalities of the two universes would create a really engaging and unique story.
In a Stranger Things and Riverdale crossover fanfiction, there are so many possibilities. The gangs from both shows could team up against a common enemy. Let's say a new evil entity that combines the characteristics of the Demogorgon and the Black Hood. The friendships and romances in the story could be completely reshuffled. Steve might have a fling with one of the Riverdale girls, or Nancy could become friends with Betty. And the settings could blend together, with scenes taking place in both Hawkins and Riverdale, creating a really engaging and unique story.
Another idea is a crossover of the Upside Down and the Weirdness of Gravity Falls. Imagine Eleven using her powers in Gravity Falls and discovering new and strange things about the town. The kids might explore areas where the laws of physics seem to be a mix of both their worlds. For example, they could find a portal that leads to a place that has elements of both Hawkins and Gravity Falls.
First, you need to know both universes well. Read the books or watch the shows carefully. Then, come up with an interesting premise for the crossover. It could be a simple as the two groups meeting by accident, or something more complex like a shared enemy. Next, focus on the characters. Decide how they will interact and what kind of relationships will form. For example, you could have Eleven and Beverly Marsh become friends. Also, think about the setting. Will it be mostly in Hawkins or Derry? Or will it be a new place? Finally, start writing and let your creativity flow.