I would recommend 'Crossover Crisis: Flash and Arrow'. This fanfiction takes the idea of a crossover to a whole new level. It not only has the main characters working together but also delves into the backstories of some of the minor characters from both shows, adding more depth to the story. It's full of action and some really cool fight scenes.
There's a fanfiction called 'Flash - Arrow: The Convergence'. In this story, the writers explore how the two different worlds of Flash and Arrow collide in a very interesting way. It shows how the characters adapt to each other's presence and how their different methods of fighting crime can either clash or work together. It's a long read but well worth it for fans of both shows.
One great Flash and Arrow crossover fanfiction is 'The City's Heroes United'. It has a really engaging plot that combines the unique abilities and personalities of the characters from both shows. The author does a great job of making the interactions between Flash and Arrow's characters feel natural.
Felicity Smoak could also be a key character. She's the tech - genius in the Arrowverse. In a crossover fanfiction, she could play a crucial role in creating a device that helps The Flash and Arrow defeat a high - tech villain. Her relationship with both heroes adds an extra layer of drama and humor.
A plot twist could be that a character from one of the shows, who seems to be a minor or unassuming figure, is actually a powerful being from the future sent to manipulate the events of the crossover. This person has been subtly guiding the actions of the heroes, and when the truth is revealed, it completely changes the heroes' perception of the events they've been through and who they can trust.
One common theme is teamwork. Since the Flash and Arrow are from different shows, fanfictions often focus on how they can combine their unique skills to fight a common enemy.
Another theme is friendship. The fanfictions usually explore the developing friendships between the characters from the two shows. They might start off a bit distrustful but then grow to respect and rely on each other. A lot of stories show how Oliver and Barry become closer friends through their shared adventures.
A good Flash and Arrow crossover fanfiction often has well - written character interactions. Since both shows have distinct characters with their own quirks, getting them to interact in a believable way is key. For example, Flash's light - heartedness against Arrow's brooding nature can create interesting dynamics.
Oliver Queen, or Arrow, is also highly popular. His skills with a bow and arrow, along with his brooding and complex personality, add a lot of depth to the crossovers. He is often the more serious and strategic one compared to Barry.
The expanded universe. The Arrow and Flash crossovers in fanfiction allow for exploration of a larger world. Writers can introduce new villains or bring in other characters from the Arrowverse. It gives fans a chance to see their favorite characters in new situations and storylines that might not be possible in the main shows.
Another theme is the exploration of different universes. Sometimes the fanfictions will send the characters into alternate realities where they have to adapt and find their way back. This allows for a lot of creativity in terms of world - building and character development. Also, friendship is often a key theme. These heroes come from different shows but in the crossovers, they form strong bonds and support each other through tough situations.
One interesting plotline could be the Flash and Arrow teaming up to face a common enemy that has powers beyond their usual foes. For example, a meta - human with the ability to manipulate time, which forces them to use their combined skills of speed and archery in creative ways.
One popular storyline is crossovers where Flash and Arrow characters team up against a common enemy. For example, they might join forces to stop a powerful meta - human or a crime syndicate that's causing chaos in both Star City and Central City. Another common plot is character development arcs. Fans often write about how a character like Oliver Queen might learn new skills or overcome personal traumas in a different way than in the original series. There are also many love - triangle - based fanfictions, such as a love triangle between Barry Allen, Felicity Smoak and Oliver Queen, which adds an interesting romantic dynamic to the existing superhero relationships.