In a 'glee and shadowhunters crossover fanfiction', perhaps there is a dark force in the Shadow World that is slowly stealing the voices of people. The Shadowhunters suspect it has something to do with a lack of positive energy. They hear about the Glee club and their ability to spread joy through music. So they bring the Glee club to their world. The Glee club members start to perform all over the Shadow World, and as they do, they notice that the voices of the affected people start to come back. But there is a catch. The dark force targets the Glee club next, and the Shadowhunters have to protect them while the Glee club continues their musical mission.
One plot idea could be that the Shadowhunters need to find a way to defeat a powerful demon that can only be weakened by a special type of music. So they seek out the Glee club. The Glee club members are hesitant at first but then realize the importance of their role. Another idea is that a spell gone wrong in the Shadowhunters' world sends some of their key characters to the Glee club's world. There, they have to adapt to high school life while also trying to find a way back. And the Glee club helps them blend in and in return, they learn about the Shadow World.
A plot could involve a Twilight vampire falling in love with a shadowhunter. The vampire has to deal with the shadowhunter world's rules about the supernatural, and the shadowhunter has to come to terms with loving a vampire, which goes against their training. This could lead to a lot of internal and external conflicts as they try to be together.
Another option is a crossover with the Harry Potter universe. The Shadowhunters could end up at Hogwarts, perhaps because there is some sort of dark magic that is spilling over into the mundane world that they need to stop. They would be amazed by the magic in the wizarding world, and there could be some funny moments as they try to understand how things work there, while also trying to keep their own identities and purposes a secret from the wizards.
One idea could be a singing competition between the Glee club and the students from Victorious. They could meet at a national music event and initially be rivals, but then start to collaborate and learn from each other's styles. For example, the Glee club could teach the Victorious crew about more traditional musical theater numbers, while the Victorious students could introduce the Glee club to more modern pop and hip - hop influenced performances.
A plot could involve a character from Glee accidentally stumbling into the Starkid universe. For example, Rachel Berry could find herself in the middle of a Starkid rehearsal. She might initially be confused but then realizes she can learn a lot from their unique style of performing. This could lead to a series of comical and heartwarming interactions as she tries to fit in and contribute to their shows.
In a 'glee and shadowhunters crossover fanfiction', the two worlds collide when Santana Lopez is out for a late - night walk and gets pulled into an alternate dimension that is the world of Shadowhunters. There, she meets Alec Lightwood. Alec is intrigued by Santana's tough - as - nails attitude. Meanwhile, back in Lima, Ohio, the rest of the Glee club realizes Santana is missing and starts to search for her. Kurt, using his fashion knowledge, discovers an ancient text that mentions a connection between music and the Shadow World. The Glee club decides to use their musical abilities as a way to open a portal to save Santana. When they finally reach the Shadow World, they find that Santana has already made a name for herself as a fearless fighter, and together they all join forces to combat a powerful demon that threatens both worlds.
One idea could be a singing competition where the groups from both 'Pitch Perfect' and 'Glee' participate. They could start off as rivals, but then gradually learn from each other's styles. For example, the Barden Bellas could teach the New Directions some of their a cappella arrangements, while the New Directions could introduce more pop and show - tune elements to the Bellas.
One idea could be that some of the Glee characters visit Mystic Falls for a singing competition. While there, they get caught up in the vampire drama. Maybe a vampire takes a liking to Rachel's voice and wants to turn her into a vampire so she can sing forever. Another plot could involve the vampires using the Glee club as a cover to hunt during their events.
A fanfiction could explore the idea of a character from Twilight becoming a Shadowhunter. For example, Bella could discover she has Shadowhunter blood and has to leave the vampire - werewolf drama behind to learn a whole new set of skills and rules in the Shadowhunter world. It would be interesting to see how she adapts and how her relationships with Edward and Jacob change as a result.
Another plot could involve an OC who comes from a long - lost line of Shadowhunters. They bring back an ancient fighting style or a forgotten weapon. This OC could be on a quest to rediscover their family's past and in the process, they end up uncovering secrets about the Shadowhunter world that could change everything. Maybe they find a hidden lair with powerful artifacts that were thought to be lost forever.
One idea could be that the characters from Glee find themselves in Central City during one of The Flash's battles. Maybe they get caught in the crossfire and The Flash has to save them while also dealing with the meta - human threat. For example, Rachel could be singing on the street when a meta - human causes chaos nearby.