One possible plot could be that Rook and Ben go on an adventure to a new planet in the Ben 10 Omniverse. They encounter a strange alien species that has a unique power. Ben tries to use his Omnitrix to transform into an appropriate alien to deal with the situation, but there are some glitches. Rook, with his Plumber skills, helps Ben figure out what's wrong and together they overcome the challenges and make new friends among the aliens.
By having them face a common enemy. When they fight side by side against a powerful foe, they can learn to trust each other more and understand each other's fighting styles better.
Yes, there are likely quite a bit. Fanfiction communities are vast and diverse. For a pairing like Ben and Rook, fans who are interested in their relationship often write stories exploring different aspects of it, from adventures they go on together to more emotional and personal interactions.
Another theme is adventure. Since they are from a universe full of strange planets and creatures, many fanfics take them on exciting adventures across the galaxy. They might be searching for a powerful artifact or trying to stop an evil force from taking over the universe. It's all about the journey and the discovery along the way.
An interesting aspect could be exploring Rook's past more deeply. Maybe he has some secrets from his time before being a Plumber that are related to the Ben 10 Omniverse. Ben could help him uncover these secrets while they are on a mission. For example, they could be investigating an ancient alien artifact, and as they dig deeper, Rook's past starts to unfold.
Another way is by showing their daily interactions. Like when they're just hanging out between missions, sharing stories about their different worlds. Ben could tell Rook about his adventures on Earth, and Rook could share stories about his Plumber training. This would make them understand each other better and grow closer. They could also have inside jokes that develop over time from these interactions. Also, having them train together to improve their combat skills would not only make them better fighters but also strengthen their relationship as they rely on each other during the training sessions.
There could also be a theme of self - discovery. As they interact, both rook and ben might discover new aspects of themselves. For example, rook might learn more about his own courage through his association with ben, and ben might understand the importance of loyalty better because of rook. This self - discovery can be a really interesting theme to explore in fanfic.
First, understand the characters of Ben and Rook well. Their personalities should shine through in the fanfic. For example, Ben's more impulsive nature and Rook's calmness. Then, use the tickling concept in a creative way, like making it a unique form of communication between them.
There probably is. Fanfiction communities are quite large and diverse. Try looking on platforms dedicated to the fandom that Ben and Rook are from. Some writers might have explored this relationship with a kiss scene in their stories.