Another great one is a story where Flash accidentally ends up in Supergirl's universe and they have to figure out how to get him back while also dealing with the villains in her world. It's interesting to see Flash adapt to a different environment and how they interact with each other's supporting characters.
A more emotional storyline could be where Flash has a premonition of Supergirl's death and tries to change the future. This delves into the complex relationship between fate and their powers, and how they struggle to overcome what seems to be an inevitable outcome. It also shows their deep bond as heroes who care about each other.
One popular storyline is when Flash and Supergirl team up to fight a common enemy from another dimension. This allows for a lot of action and showcases their different powers working together.
Another interesting idea is a mind - control situation. A powerful telepath takes control of some of the heroes and villains in their respective cities. Flash, Arrow, and Supergirl have to find a way to break the mind - control. They start by finding the source of the telepath's power. Along the way, they discover that the telepath has a tragic past that led to this misuse of power. They try to reason with the telepath while also fighting off the controlled allies and villains.
One idea could be that a powerful villain threatens both their cities simultaneously. Supergirl and The Flash have to team up, and in the fanfiction, their different powers and personalities could lead to some interesting interactions. For example, Supergirl's strength and The Flash's speed could be combined in unique ways to defeat the villain.
One popular storyline is where Flash and Supergirl team up to fight a common, powerful enemy like a super - villain from another dimension. They combine their speed and strength in unique ways to save the world. Another is a more character - driven plot where they develop a romantic relationship. Flash's quick - witted charm and Supergirl's strong - willed nature make for an interesting dynamic. There are also storylines where they swap powers temporarily, leading to humorous and action - packed situations as they learn to use each other's abilities.
Another great storyline could involve a cross - dimensional rift that brings characters from Arrow's world into Supergirl's and vice versa. This would create a lot of chaos as the characters have to adapt to the different rules and environments. For example, Oliver might struggle with the presence of aliens in Supergirl's world, while Kara has to deal with the more gritty and crime - ridden Star City. It could also lead to some interesting character pair - ups and new friendships or rivalries.
One interesting storyline could be a team - up where Supergirl and The Flash have to stop a powerful villain from another dimension. They use their combined powers of super - speed and super - strength to outwit the bad guy.
One interesting storyline could be a team - up against a powerful new villain that neither The Flash nor Supergirl can defeat alone. They have to combine their powers and strategies in a way they've never done before.
A great moment could be when they first meet and realize how different yet similar their worlds are. Supergirl might be in awe of The Flash's speed, and The Flash could be impressed by Supergirl's strength. It's a moment of mutual respect that often sets the tone for the rest of the story.
Well, Cisco Ramon from The Flash would be a great addition. He could use his tech skills to create some new gadgets or figure out ways to counter the villains' powers. Also, Martian Manhunter from Supergirl's side. His shape - shifting and telepathic abilities would add a whole new dimension to the story.
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.
Perhaps in this fanfiction, Barry's death causes a rift in the multiverse. Supergirl then has to team up with other heroes from different universes to try and fix it. His death could be the start of a much larger threat that only a united front of heroes can face. She might struggle with the guilt of not being able to save him at first but then turns that into motivation.