One common theme is the exploration of power dynamics. When the X - Men cross over with other groups, like the Avengers or the Fantastic Four, there's always a comparison and contrast of their powers. For example, in a crossover with the Avengers, the mutants' powers might be seen as more unpredictable compared to the technology - based powers of some Avengers.
There's also 'X - Men and the Fantastic Four: A Mutant Alliance'. In this fanfiction, the X - Men team up with the Fantastic Four. It delves into how the two groups, with their different powers and personalities, work together. There are some really fun moments as they try to figure out how to combine their abilities to face various threats.
Another plot could involve a misunderstanding between the two groups. Maybe some of the Avengers misunderstand the X - Men's mutant powers as a threat and start a conflict. But then they realize they were wrong and join forces to face a real villain who was secretly manipulating the situation. This would involve a lot of character development and relationship building among the different heroes.
Storm and Thor could make a powerful duo. Both have control over powerful natural forces, Storm with the weather and Thor with lightning and thunder. Their powers could be combined in unique ways to take on powerful enemies. Also, they could have an interesting cultural exchange as Storm is from Africa and Thor is from Asgard.
The combination of powers. You get to see the superpowers of the X - Men, like Jean Grey's telekinesis and Cyclops' optic blasts, interact with the powers of the Avengers such as Thor's lightning and Captain America's super - strength. It makes for some really epic battle scenes.
One great 'xmen and avengers crossover fanfic' is 'The United Front'. It has an exciting plot where the X - Men and the Avengers have to team up against a common enemy from another dimension. The character interactions are really well - written, especially the banter between Wolverine and Iron Man.
One great Xmen teen reader fanfiction is 'X - School Days'. It focuses on a new teen mutant arriving at the X - Men's school and their journey of self - discovery. The characters are well - written and it has a lot of heartwarming moments.
Batman himself is obviously very popular. His dark and brooding nature contrasts well with the more colorful X - Men world. Also, Wolverine is often a fan favorite in these crossovers because of his tough - guy attitude.
One interesting crossover could be Batman teaming up with Wolverine. Their different fighting styles, Wolverine's brute strength and healing factor along with Batman's gadgets and strategic mind, would make for an exciting story.
The plot could involve Superboy getting lost in the X - Men's universe. He has to figure out how to get back home while also getting involved in the X - Men's internal conflicts. Maybe there's a power struggle within the X - Men group and Superboy's outsider perspective helps to resolve it. At the same time, he has to deal with the fact that his powers are different from the mutants and some may see him as a threat or an oddity.