What are some popular 'Ben Ten' adult fanfics?

Definitely. There are many well - written 'Ben Ten' fanfics that are suitable for all ages. Some might take an existing story arc from the show and give it a new twist. For example, they could change the outcome of a battle or introduce a new character that affects the dynamics between Ben, Gwen, and Kevin. Others might explore what would happen if Ben lost his Omnitrix and had to rely on his wits and the help of his friends more. These fanfics can be really engaging and add new depth to the 'Ben Ten' universe.

Rather than focusing on adult fanfiction, which is not something that should be promoted in a general context, we can consider fanfictions that deal with the relationships between Ben and his friends in a more emotional and complex way. For example, how they support each other during difficult times, or how they grow together as a team. This kind of fanfiction can add a lot of depth to the Ben 10 story.

Some 'Ben 10' fanfics might revolve around alternate universes. In these fanfics, Ben could be a villain instead of a hero. It would be a really cool concept to see how his different alien forms are used for evil rather than good. Also, there could be fanfics that deal with the origin stories of the aliens in more depth. Like exploring where the Omnitrix really came from and what kind of ancient technology was involved in its creation.

Writing fanfiction with adult themes is not appropriate and goes against many ethical and content guidelines. So, I can't provide relevant themes.

One popular plot twist is when Ben and Gwen end up in a different dimension where their roles are reversed. So, Gwen has something like the Omnitrix and Ben has to rely on his wits and basic combat skills without alien forms. This forces them to adapt in new ways and understand each other's struggles better.

Some popular ones might be those that explore new adventures for Ben and his alien forms. For example, fanfics where Ben discovers a new alien species on a previously uncharted planet. These often involve his Omnitrix malfunctioning in interesting ways, leading to unexpected transformations and challenges.

One popular theme could be alternate universes where the characters have different powers or relationships. For example, an AU where Ben's alien forms have unique social structures among themselves. Another theme might be character growth and development into adulthood, dealing with more complex emotions and responsibilities compared to the original series. Also, crossovers with other science - fiction universes can be a theme, like Ben 10 meeting characters from Star Trek.

One popular theme could be alternate universes where the characters have different powers or relationships. For example, an AU where Ben has to deal with his powers in a more adult - like world full of political intrigue related to the Omnitrix. Another theme might be character growth and development into adulthood, like how Gwen would handle her magical powers as an adult in a more complex society. And also, there could be themes of love and relationships, perhaps exploring Ben's romantic relationships in a more mature way compared to the original series.

I'm not sure specifically which ones are the most popular. However, you can try searching on fanfic platforms like FanFiction.net or Archive of Our Own. Usually, the ones with high ratings and a lot of reviews might be popular among fans.

Some fanfics might also take a more creative turn, such as giving them new powers or putting them in a completely different setting, like a steampunk world. This allows for a fresh take on their characters and the stories that can be told about them.