Another plot could involve Stark time - traveling to key moments in his own life. For instance, he travels back to when he first started Stark Industries and makes different decisions about the direction of the company, which then has a huge impact on the future of the world in terms of technology, superhero relations, and global politics.
Maybe Stark travels to the future and discovers a world where his technology has been misused to the extreme. He then returns to his own time determined to set safeguards to prevent such a future. He could start new research projects focused on ethical technology use.
One idea could be that Tony Stark travels back in time to prevent the creation of certain dangerous technologies that later cause chaos in his timeline. He could use his genius to subtly alter the course of scientific development.
Maybe all the Starks, including Pepper and Morgan, travel back to the time when Howard Stark was starting out in business. They could help him with modern knowledge, and in the process, they might accidentally change some key events that lead to unforeseen consequences, like a new kind of Iron Man suit being created much earlier.
One plot idea could be that Jon and Sansa travel back to the time before their family's downfall. They could use their knowledge of future events to prevent Ned Stark's execution. For example, they might be able to expose Littlefinger's schemes earlier. Another idea is that they travel to a future time where the White Walkers have been defeated, but they find new threats emerging and have to figure out how to deal with them. They could also travel to different kingdoms in different eras and learn about different cultures and forms of governance, which could then help them better rule Winterfell and the North.
Well, perhaps Tony Stark time - travels during the Civil War to a moment when he first started developing Ultron. He then uses his future self's wisdom to avoid creating Ultron in the first place. This would change the entire dynamic of the Civil War as the destruction caused by Ultron was a major factor in the public's distrust of the Avengers. He could also time - travel to meet a younger version of Captain America and try to understand his point of view better from the start.
One idea could be Arya traveling back to the time before her family's downfall. She could use her skills to prevent certain events from happening, like Ned Stark's execution. Maybe she'd change the course of battles by secretly assassinating key enemies.
One idea could be that Tony Stark's daughter discovers a hidden time - travel device in her father's old workshop. She decides to use it to go back in time to prevent her father's death. Along the way, she meets younger versions of the Avengers and has to convince them to help her without revealing too much about the future.
Maybe she travels to a time during a great war. She could end up changing the course of the war by providing crucial information or by using her skills in a way that no one expected. For instance, if she found a way to counter an enemy's powerful jutsu that was thought to be unbeatable at that time. This would not only affect the outcome of the war but also change the future of the ninja world she came from.
One idea could be a story where Tony discovers a hidden diary of Howard's that reveals secrets about his early inventions and the true motives behind some of his actions. This could lead to Tony having a new perspective on his father and his own work.
One idea could be that Sansa goes back in time and tries to prevent the Red Wedding. She could use her knowledge of the future to warn her family and change the course of that tragic event.
One idea could be Madara traveling back to the era of the Sage of Six Paths. He could try to change the very foundation of ninjutsu, which would create a whole new timeline. Maybe he would attempt to gain the power of the Sage for himself much earlier in history.
Well, perhaps a time - traveling device accidentally sends Judy Hopps back to a time when prey and predator relations were extremely tense. She has to use her wits and modern - day knowledge to prevent a major conflict that could have changed Zootopia's future for the worse. Or, a time - traveling fanfiction could focus on Nick Wilde going back to his own past, where he can make different choices that would impact his relationship with Judy and his standing in Zootopia society in the present.