How about a crossover between the Guardians of the Galaxy and the Inhumans? The Guardians' wacky, space - faring adventures could intersect with the Inhumans' more earth - based, but still otherworldly, powers. Star - Lord and Black Bolt trying to communicate could be both hilarious and intense.
One great idea could be a crossover between the X - Men and the Avengers. Imagine Wolverine teaming up with Captain America, their different fighting styles and moral compasses would create an interesting dynamic. Wolverine's rough - and - tumble, lone - wolf approach contrasting with Captain America's more traditional leadership and sense of justice.
Another possibility is that a Marvel hero, say Spider - Man, accidentally ends up in Beach City. He teams up with Steven to deal with a local threat that is also related to some sort of interdimensional chaos. For example, a group of villains from the Gem world and the Marvel world are working together to open portals to other dimensions to steal valuable resources. Steven and Spider - Man would have to use their unique abilities to stop them.
One great DC Marvel crossover fanfic is 'The Avengers and the Justice League: United Front'. It has an exciting plot where the two teams come together to fight a common, powerful enemy. The character interactions are well - written, especially the exchanges between Superman and Captain America, who share similar leadership qualities.
There's also 'The Flash and Quicksilver: A Race of Worlds'. This fanfic focuses on the two speedsters from different universes. They start off as rivals but then become friends as they face a threat that only their combined speed can defeat. It has some really cool scenes with their super - speed abilities.
One idea could be Ben Tennyson using his Omnitrix to team up with Spider - Man. Ben could transform into XLR8 to chase down villains while Spider - Man swings through the city. Another could be having Four Arms help the Hulk in a battle, combining their brute strength. And perhaps Heatblast could join forces with the Human Torch to fight a fire - based villain.
One idea could be a story where the Avengers and the Justice League team up to fight a common enemy like Darkseid and Thanos working together. Another could be a character - swap scenario, for example, Superman being in the Marvel universe and having to deal with the likes of Doctor Doom. Maybe a story where Batman uses his detective skills to solve a mystery in the Marvel world that involves Hydra.
One idea could be to have the ponies from MLP end up in the Ninjago world. Maybe Twilight Sparkle could use her magic to help the Ninjas in a big battle against an ancient evil. The contrast between the colorful and magical ponies and the more martial arts - based Ninjago characters would create an interesting dynamic.
A Stranger Things crossover fanfic with the Avengers would be really exciting. The Hawkins kids could team up with the Avengers to fight off the Demogorgon which has somehow become a threat to the entire world. Or a crossover with Doctor Who. The Doctor could land in Hawkins and help the gang deal with the Upside Down, bringing his unique time - traveling and alien - fighting skills. Also, a crossover with the Ghostbusters would be fun. They could come to Hawkins to deal with the strange entities from the Upside Down using their proton packs.
One idea could be that Master Chief gets transported to the Marvel universe. He teams up with the Avengers to fight a common enemy like Thanos who has somehow obtained Covenant technology. His Spartan abilities would be a great addition to the team.
Well, a cool concept would be for Luke Skywalker to end up in the Marvel universe and train some of the young superheroes in the ways of the Force. Or perhaps the X - Men could find themselves in a conflict in the Star Wars galaxy, with their mutant abilities adding a new dynamic to the Star Wars battles.
One plot idea could be Master Chief getting transported to the Marvel Universe. He could team up with the Avengers to fight a common threat like Thanos. His advanced combat skills and Spartan armor would add a new dynamic to the team. Maybe he'd be initially distrusted, but prove his worth in battle.