It could be about Rook having some sort of adventure while meeting Ben's babies. Maybe he helps protect them from a threat or teaches them some unique skills.
Well, perhaps it involves Rook coming across Ben's babies in an unexpected place. He might be initially confused but then quickly bonds with them over some shared experiences or interests. For example, if the babies have some special powers like Ben, Rook could be intrigued and try to understand how to help them control or develop those powers.
The plot might revolve around Rook being assigned a mission that somehow involves Ben's babies. He could be tasked with looking after them for a while. During this time, they get into all sorts of mischief together. Rook tries to keep them safe while also learning a lot about their personalities. He might find that the babies have a different perspective on things compared to Ben, which could lead to some interesting character development for Rook as he adapts to dealing with them.
The main characters are Rook and Ben's babies. Rook, who might be from a different background or with different abilities, is the one who is going to interact with the babies. The babies, on the other hand, could have inherited some of Ben's traits. Their interactions will form the core of the story. For instance, if Ben has superpowers and the babies show some signs of those powers, Rook will have to deal with that while getting to know them.
In this fanfiction, it could be that the Necrofriggian babies are the result of some sort of experiment gone wrong. Ben stumbles upon them and realizes that he is the only one who can help. He has to figure out how to reverse the effects of the experiment while also dealing with the fact that the babies are in a very fragile state. He might enlist the help of his friends, but also face challenges from those who don't want the experiment to be reversed.
Perhaps a story where an old enemy of Ben's targets Rook to get to Ben. Ben feels guilty and protective. They go on the run, hiding in different places across the galaxy. Along the way, they meet some interesting characters who help them. In the end, they face the enemy together, with Ben using his Omnitrix and Rook using his upgraded Proto - Tool to defeat the bad guy.
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.
The fanfic might revolve around the Big Chill babies being in a situation where they need to protect something precious. It could be an ancient artifact that has the power to either save or destroy their part of the universe. They have to use their cold - based powers, like shooting ice blasts or creating ice shields, to fend off villains who want to use the artifact for evil purposes. Along the way, they might meet some of Ben's other alien forms and team up with them to achieve their goal.
Another possible antagonist could be an alien scientist who was involved in the creation or discovery of the Necrofriggian babies. This scientist might have his own evil plans for the babies and sees Ben as an obstacle in his way. He could be using his advanced technology to try and capture the babies from Ben.
Friendship is a very common theme. Their bond as partners in protecting the universe is often explored in depth.
The friendship between Ben and Rook is a big draw. In fanfiction, it can be explored in different ways, like in tough situations or during their downtime. Also, the alien - filled universe of Ben 10 provides a lot of scope for interesting stories. Writers can create new alien species or new powers for Ben's Omnitrix, and Rook's Plumber skills add another layer of complexity to the stories.
Another theme is growth. Both characters can grow and learn from each other. Ben might learn more about Rook's culture and values, and Rook can learn about Ben's more impulsive but brave nature. This mutual growth helps to strengthen their relationship in the fanfiction stories.
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.