Power and responsibility is also a big theme. Ben has to handle the powers of his alien forms responsibly, especially when dealing with aliens. In many fanfics, there's also the theme of discovery. Ben discovers new things about the aliens, their cultures, and their abilities. For example, he might learn a new power from an alien that he can use in a different way. There's also the theme of cooperation, where Ben and the aliens work together to achieve a common goal, like saving a planet or stopping a powerful enemy.
Well, there's 'The Alien Bond'. In this fanfic, Ben Tennyson forms a very special bond with an alien that has the power to manipulate time. It's really interesting as it shows how their relationship develops and how they use their combined powers to face various challenges. There are also some fanfics that explore what would happen if Ben could communicate with his alien forms on a more personal level, like in 'Ben and the Sentient Aliens' where the aliens have their own personalities and thoughts that Ben has to deal with.
One common theme is friendship. The OC and Ben often form a strong bond of friendship through their adventures. Another is self - discovery. Both the OC and Ben might learn new things about themselves when they are together. And power - combination is also common, like how their different powers work together.
Gwen would be a great character to pair with Alien X. Her magical abilities could complement Alien X's powers in interesting ways. For instance, when facing a threat that requires both brute omnipotent force and the finesse of magic. Another good pairing could be Kevin. His ability to absorb and use different forms of energy could interact with Alien X's power source in unexpected ways, like when they need to combine their powers to break through a powerful energy barrier.
Well, 'Star - Crossed with Ben Tennyson' is a must - read. It has an interesting take on the relationship, with the reader character coming from a different world and how they and Ben deal with the cultural differences. And 'Love Among the Aliens' is really good too. It shows a more mature side of the relationship between Ben and the reader, dealing with issues like trust and loyalty in a very engaging way.
One popular 'ben tennyson x oc fanfic' is 'The New Ally'. It has an interesting plot where the OC has unique powers that complement Ben's. Another is 'A Different Perspective' which delves into how the OC changes Ben's view of things in his adventures. And 'OC's Impact' shows how the OC affects the relationships within the Ben 10 universe.
Maybe in the fanfic, Ben Tennyson is handcuffed as part of an experiment gone wrong. He has to figure out how to use his alien powers in a limited way with his hands cuffed. His struggle could be about not only getting free but also saving the day from the chaos the experiment created.
Another possibility is a rogue member of the Plumbers (the organization Ben sometimes works with). This character might feel that Ben is too powerful and a threat, so he handcuffs Ben to try and contain him. This would lead to a conflict within the Plumbers' ranks as Ben's friends try to free him and figure out why this has happened.
To write a good 'Ben Tennyson x Reader' fanfiction, you need to focus on their relationship development. Start with how they meet and gradually build up the chemistry between them. Make use of the Omnitrix and Ben's alien forms in the story to add some action and excitement. For instance, the reader could be in danger and Ben has to transform into one of his aliens to save them. And don't forget to add some emotional depth to their interactions.
I'm not entirely sure as I haven't read that specific fanfiction. But generally, in Ben 10 related fanfiction, it might involve creative and often alternative storylines about Ben Tennyson and Gwen Tennyson's relationship, perhaps with some unique adventures or character developments.