One exciting plot twist could be the unexpected alliance between characters from different Arrowverse shows against the Infinity War - like threat. For example, if The Flash's team joined forces with Supergirl's group in a completely new way. Another might be a character from a less - known part of the Arrowverse turning out to be the key to victory. Maybe a character from Legends of Tomorrow has a hidden power that can defeat the powerful villains in this fanfic version of Infinity War.
They blend elements by having Arrowverse characters use Infinity War - inspired tech or powers. For example, a character might get their hands on a version of the Power Stone and it gives them new abilities. Also, the settings can be a mix. You might see a battle take place in Star City but with the kind of epic scale and alien presence like in Infinity War.
In Infinity War fanfiction, Loki can be alive. Fanfic authors have the creative liberty to rewrite the events. They might bring Loki back to life using magic or some other means. For example, Loki could have faked his death and gone into hiding, only to reappear later in the story to help the heroes fight against Thanos. His survival can add an interesting twist to the story and create new interactions between characters.
Well, it would be much more light - hearted in many ways. The Cartoon Network characters have a different style of humor and action compared to the serious and often dark tone of the original Infinity War. For instance, the Powerpuff Girls would bring a sense of girl - power and sassy dialogue, which is quite different from the brooding heroes in Marvel's Infinity War.
Well, in this fanfiction scenario, if Wanda could reverse the snap, it would be a game - changer. Vision was a key part of her life, and her love for him could fuel this power. But it wouldn't be easy. There would be a huge energy cost, and she might have to sacrifice something in return. Maybe she'd have to give up some of her own life force. And then there's the matter of Thanos. He wouldn't just stand by and let her undo his 'work'. There would be a massive battle, and the outcome would be uncertain.
One way to 'fix' the situation in a fanfiction could be to have Loki's faked death in Thor: The Dark World be more thoroughly investigated by Thor. If Thor had been more suspicious and dug deeper, he might have uncovered Loki's real plan earlier. This could have led to them working together more effectively against Thanos in Infinity War, preventing some of the tragedies that occurred.
In most cases, it is legal. Fanfiction is a form of creative expression by fans. As long as it doesn't violate any copyright laws in a major way, like using the exact same footage from the trailer without permission in a way that undermines the original work's marketability. But if it's on a legitimate platform that respects intellectual property, you should be okay.