Their relationship could start as a simple acquaintance at Hogwarts. As they participate in school activities like Quidditch matches or wizard duels, they gradually become friends. Then, as they grow older, they might realize they have deeper feelings for each other.
One possible storyline could be them going on an adventure in the wizarding world together. They might discover a hidden magical artifact and have to protect it from dark wizards. Another could be a story about their friendship growing over time as they attend Hogwarts and face various challenges together, like dealing with difficult professors or school bullies.
James might be really excited. He's heard stories about his father's friends, and Teddy is like a link to that past. He'd probably be full of questions about the Marauders and what his dad was like as a student. Lily, on the other hand, would be more reserved but still interested. She might be a bit more empathetic towards Teddy, considering his difficult past. Overall, they'd both be curious and eager to learn more from him.
One possibility could be that Teddy is visiting Hogwarts for some event, perhaps a special anniversary celebration. James and Lily, being students at Hogwarts, cross paths with Teddy. Teddy, being the son of Remus Lupin and having a connection to their family through Harry Potter (James and Lily's son), might share some interesting stories about their parents' time at Hogwarts. Maybe he tells them about the Marauders and how their father and his friends were quite the mischief - makers. It could be a heartwarming encounter where James and Lily get to see a different side of their family's history through Teddy.
Perhaps there's a prophecy about Lily Luna Potter that Teddy overhears. This makes him extremely overprotective as he believes she's in great danger. The fanfiction could then revolve around them trying to figure out how to prevent the prophecy from coming true, with Teddy constantly hovering over Lily Luna and her getting frustrated with his over - protectiveness at times. It could also involve other characters from the wizarding world who either help or hinder their efforts.
There could be a fanfiction where Lily Luna Potter is involved in some sort of magical mystery, and Teddy, being overprotective, jumps in to help. For example, if there's a new dark magic item discovered on the Hogwarts grounds. Teddy would be by Lily Luna's side, using his metamorphmagus abilities to their fullest to keep her safe while they figure out what's going on.
She might meet her father, Harry Potter, when he was still a student at Hogwarts. This would be an amazing encounter as she could see a side of her father she never knew before.
A possible fanfiction could involve Lily Luna Potter and her time - traveling adventures. She accidentally stumbles upon a time - turning device and gets sent back to the time of the first Wizarding War. There, she has to be careful not to disrupt the timeline while also trying to learn from the events of that time to prevent a similar future catastrophe.
Well, it really depends on the fanfiction author's creativity. Some might give her a Patronus that reflects her own unique personality traits. For example, if she's portrayed as very brave and fierce in a particular fanfic, her Patronus could be a lioness, representing her courage and leadership. Another possibility is that it could be a bird, perhaps a phoenix, which would tie in with the magical and powerful nature often associated with the Potter family.
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.