One idea could be that the characters from Riverdale somehow find themselves in the wizarding world of Harry Potter. Maybe Jughead could be a Muggle - born wizard who discovers his powers while at Hogwarts. He might write about his strange new experiences in his journal, just like he does in Riverdale.
One popular theme is Sabrina crossing over with other magical universes. For example, a crossover with Harry Potter could involve Sabrina attending Hogwarts and interacting with the students there. Another theme is a crossover with fairy - tale characters. Sabrina might meet Cinderella or Snow White and get involved in their stories. Also, a modern - day crossover where Sabrina enters the world of a popular TV show like 'Stranger Things' can be really interesting, with her magic causing chaos in the Upside - Down.
One way it could work is if there was a time - travel or multiverse plot. For instance, Arrow characters could accidentally end up in Riverdale's time period or vice versa. They would then have to figure out how to get back while dealing with the local problems. Maybe Green Arrow has to help solve a mystery in Riverdale that's related to his own enemies in some way.
In a Riverdale and Arrow crossover fanfiction, the story could start with some sort of interdimensional rift that pulls characters from both shows into one world. Riverdale characters would be shocked by the violence and danger in Arrow's world. Meanwhile, Arrow characters might find the high school drama and relationships in Riverdale quite strange. There could be a big bad villain that only the combined skills of both groups can defeat. They would have to learn to work together despite their differences, and along the way, there could be some romantic subplots between characters from the two shows as well.
Hermione Granger from Harry Potter would be an interesting pair. Hermione is highly intelligent and knowledgeable about magic, while Sabrina has her own unique brand of magic. Their interaction could involve Hermione trying to understand Sabrina's more chaotic magic, and Sabrina learning from Hermione's book - smarts. Another great pairing could be Buffy Summers. As a vampire slayer, Buffy has a different kind of strength and purpose, and her world of demons and vampires would contrast with Sabrina's more traditional witchcraft world.
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.
Well, Archie might befriend Harry Potter. They both have a sense of justice and are brave. Archie could introduce Harry to football (or soccer as it's known in some parts of the world), and Harry could show Archie how to play Quidditch. Betty and Hermione could bond over their intelligence and love for books. They might study together in the Hogwarts library.
In some 'Riverdale Crossover Fanfiction', a crossover with a time - travel plot is really engaging. For example, when the Riverdale gang travels back in time to the 1950s and has to deal with the different social norms while also trying to get back to their own time. Also, crossovers with other teen drama shows where they have to compete in a singing or dancing competition together can be quite entertaining.
There are many out there. A popular 'Riverdale Crossover Fanfiction' involves a crossover with the 'Chilling Adventures of Sabrina'. The dark magic elements from Sabrina's world add a new dimension to Riverdale's already complex story. You can find these fanfics on websites like Archive of Our Own. Just search for 'Riverdale Crossover' and you'll get a ton of options.