It could be a time - traveling version of one of his existing villains. For example, Zoom could have found a way to travel back in time and is trying to change history to make his own future more powerful. Another option is that a new character, a time - keeper type of villain, emerges. This villain's goal is to stop Barry from messing with the timeline and will do anything to preserve the original course of history, even if it means harming Barry.
One idea could be that Barry goes back in time and accidentally changes a small event that has huge, unforeseen consequences in the present. For example, he might prevent a minor accident that then leads to a different person becoming a supervillain. Another plot could be that he goes back to meet a deceased loved one and has to struggle with the ethics of changing their fate. Or perhaps he goes back to his own childhood and tries to give himself advice, but realizes that changing too much could erase his present self.
Barry Keoghan's back story involves his early life in Ireland. He faced hardships while growing up. Being in foster care, he had to navigate through a lot of challenges at a young age. His experiences have made him a more empathetic actor, and it shows in his performances where he can portray complex emotions very well.
Well, it could be that Brittany started running as a way to get in shape. As she continued running, she gradually built up her endurance and distance. Maybe she joined a running group where she got the motivation and support to take on the challenge of a marathon. She might have also had a bet with a friend or family member which pushed her to train hard for it. And along the way, she overcame various obstacles like minor injuries and self - doubt.
I'm not entirely sure specifically what 'rahdo runs through time stories' is. It could be a unique storytelling concept, perhaps a series where someone named Rahdo is involved in stories that have a time - related theme. It might be about adventures through different historical times or some sort of time - traveling tales.