Another explanation could be that Teddy discovers an ancient and forgotten spell or artifact. He stumbles upon it while exploring some old wizarding ruins or in the Hogwarts library. This spell or artifact gives him the power to travel through time. And as he's always been an adventurous and curious character, he decides to use it to explore different time periods.
It could be that Luke has a unique connection to the Force that gives him the power of time travel. He might have to enter a deep meditative state, and during this trance, he can project his consciousness through time. If he wants to physically travel, he has to use a great deal of his Force strength to fully materialize in another time.
Well, their relationship would be complex yet beautiful. Since Teddy is just a baby, Hermione would have to take care of all his basic needs. As they travel, Hermione would start to teach Teddy about different magical things she discovers in each time period. Teddy would be curious and his innocent questions would make Hermione think more deeply about magic. This exchange would deepen their relationship. Also, as they face challenges together, like when they are misunderstood in a certain time period or when they have to face powerful wizards, they would become closer. Teddy would see Hermione as his hero, and Hermione would see Teddy as a precious charge she needs to protect and nurture.
One idea could be that Baby Teddy Lupin time - travels back to the Marauder era. He could meet his father, Remus Lupin, as a young boy. This would create some really heartwarming and bittersweet moments as Teddy gets to see his father's early life and perhaps even influence some events in a positive way.
Sasuke would be suspicious at first. He's not one to trust easily. But once he realizes it's Naruto, he might see it as an opportunity to gain some new knowledge or power. He could also be a bit envious that Naruto has this time - traveling ability, thinking it gives Naruto an even greater advantage.
He could also form a pact with a time - based entity. By making a deal with a being that exists outside of normal time, Doctor Strange might gain enhanced time - travel powers. But this would come with its own risks, like being indebted to this entity. He would have to be very careful about the terms of the pact.
In some Harry Potter fanfictions about Teddy Lupin's time travel, he might go back to prevent certain tragedies. For example, he could try to save his father Remus Lupin from the final battle. He might use his knowledge of the future to change the course of events, perhaps by warning the Order of Phoenix earlier about Voldemort's plans.
One interesting story could be where Teddy Lupin travels back in time to meet his parents. He gets to experience their lives firsthand and maybe even change some small things that have a big impact on his own future. It could be a heartwarming tale of family connection.
Luffy's abilities would be quite different in Roger's time. His rubber powers would be something unheard of. He would likely be seen as a very strange and powerful individual. Roger and his crew might be both intrigued and cautious around him. His Gear techniques would be a huge advantage as no one in that era would have seen anything like it.
Obviously, Teddy Lupin is the central character. But often, his family members from the past like his father, Remus Lupin, and his mother, Tonks, are also involved. Their relationships and how Teddy interacts with them in the past are key elements of the story.
When Harry and Teddy time travel, Harry could become more open - minded. He has been through a lot in his own time, but seeing different cultures and ways of life in other time periods would shatter some of his preconceived notions. Teddy would mature faster. Imagine traveling to a time of great turmoil in the wizarding world. Teddy would have to step up, make decisions, and face consequences. This would transform him from a somewhat carefree young wizard into a more responsible and strategic one. Harry, too, would learn from Teddy's growth and vice - versa, strengthening their bond and further developing their characters.