RM would probably be very analytical. He'd immediately start thinking about how to use this opportunity to improve their group's past mistakes and make better strategic decisions. For example, he might focus on getting more international exposure earlier.
Well, in the world of 'back in time fanfic', there are stories that take characters back to the Victorian era. In these, the characters might be dealing with strict social hierarchies. They could be a modern - day person suddenly in a world where propriety and etiquette are of utmost importance. This can lead to all sorts of interesting situations, like trying to hide modern - day ideas while also trying to fit in and perhaps change some things for the better.
One great 'Percy sent back in time' fanfic is 'Back to the Beginning'. It shows Percy having to deal with all the early threats in a new way. Another is 'Time - Twisted Percy' which has an interesting take on how his knowledge of the future changes things. There's also 'Percy's Time - Travel Adventure' where he forms unexpected alliances in the past.
First, do your research. If you're sending a character back to, say, the Renaissance, know about the art, the politics, and the daily life then. Second, create a strong character arc. The character should grow or change because of their time - traveling experience. For example, they might start off as a spoiled modern kid and become more self - reliant in the past.
In the 'Percy goes back in time fanfic', he may also meet his younger self. This could lead to some really interesting and confusing situations. He would have to be careful not to disrupt the timeline too much while still achieving whatever his goal is for going back in time.
His friends from his normal time period could also be important. They might be the reason he decides to go back in time in the first place, like to save one of them from a past danger.
There are many fanfics that play with the idea of time travel. For Bella going back in time to meet Jasper, the story could explore how their prior knowledge of each other in the future affects their initial meeting in the past. For example, does Bella already trust Jasper because she knows him from the future? This could create a really unique dynamic in the story.
It could be Orochimaru. Since Orochimaru has always been interested in power and immortality, if Naruto goes back in time, Orochimaru might sense the change in the timeline and try to stop Naruto from changing things that could affect his future plans for power.
One possible plot could be Anakin going back to a time before his fall to the dark side. He could use his knowledge of the future to prevent certain tragedies. For example, he might stop the Clone Wars from starting, thus saving countless lives. This would also give him a chance to redeem himself and perhaps even change the fate of the Jedi Order.
One common theme is self - discovery. When Percy is sent back in time, he often has to re - evaluate who he is without all the experiences he had in his original timeline. Another theme is the butterfly effect. His actions in the past can have huge consequences for the future. For example, a small decision he makes might change the entire course of a battle.