Well, here's a plot. A new villain emerges who has the ability to absorb energy. He targets Superman first, draining his solar - powered strength. Flash tries to stop him but realizes he's outmatched. So, Flash decides to run around the Earth in reverse to turn back time and warn Superman before the attack. Another could be that Flash discovers a Kryptonite - like substance that affects Superman in a different way. He has to decide whether to keep it a secret or tell Superman, all while they're dealing with a threat to Metropolis.
One idea could be a race between Superman and Flash that gets disrupted by a common enemy. They then have to team up to defeat this foe while also dealing with their friendly rivalry.
One plot idea could be that Superman and Catwoman are forced to team up against a common enemy, like a powerful alien or a supervillain who is threatening both Gotham and Metropolis. During their partnership, they start to understand each other's motives and develop an unexpected bond.
One idea could be that Protozoa, being a microscopic organism in nature, has some sort of special connection to Zenon. Maybe Protozoa is a sentient being in this fanfiction and can communicate with Zenon telepathically. Zenon could be on a scientific mission to study Protozoa but ends up learning life - changing lessons from it.
One idea could be that Goofy and Minnie are accidentally paired up for a dance competition. They initially struggle because of their different styles but gradually learn from each other and form an unexpected friendship. Another plot could be set in a world where all the characters' personalities are swapped, and Goofy is super sophisticated while Minnie is a bit of a klutz. They meet and have to navigate this strange new dynamic. A third idea is that they both discover a hidden magical place in the Disney universe and have to work together to protect it from a threat, with their unique skills and quirks coming into play.
A more light - hearted plot could be that Pitch accidentally gets frozen by Elsa's powers. When he thaws, he finds that he has lost some of his dark powers. In order to get them back, he has to 'befriend' Elsa. Through this forced friendship, they both learn about each other's insecurities and fears, and in the end, Elsa helps Pitch find a new purpose that doesn't involve spreading fear.
One plot idea could be that Pennywise and the Babadook team up to haunt a small town in a unique way. They combine their powers of fear - Pennywise with his shape - shifting and the Babadook with his dark, shadowy presence. Another could be a battle between them for the most feared entity title, which causes chaos in the spiritual realm they inhabit. And perhaps they both target the same person who has a special ability to see and interact with them, leading to a strange alliance between the victim and one of them against the other.
Well, they could be involved in a mystery - solving plot. A strange phenomenon is occurring in their world, like animals are disappearing or plants are turning into stone. Rayman and Globox become detectives of sorts. They follow clues, which lead them to an old, forgotten part of their world. There, they discover that an ancient evil has been awakened and is causing all the chaos. To stop it, they have to combine their unique skills, with Rayman's agility and Globox's strength (and his ability to eat almost anything to get out of tight spots), to defeat the evil.
Maybe the OC is a scientist who has developed a device that can temporarily steal The Flash's speed. At first, the OC uses it for personal gain, but then realizes the chaos it's causing in the city. They then team up with The Flash to take down other villains who are after the device. Or, the OC could be a meta - human with the ability to see the future in flashes. The Flash initially doesn't trust the OC, but as they start to have the same visions, they have to work together to prevent a major disaster from happening.
One idea could be a story where the reader is a new hero in the Injustice 2 universe. Superman, initially suspicious, starts to see the good in the reader. As they team up against common threats, a bond forms between them. Maybe the reader has a unique power that Superman comes to rely on.
A good plot could be that the world is suddenly hit by a wave of anti - superhero sentiment. Wonder Woman and Superman are two of the main targets. They have to go undercover and live among the humans for a while. During this time, they learn more about the regular people's fears and concerns. They also start to develop a romantic relationship as they rely on each other for support in this difficult situation.