A possible plot could involve an alternate universe. In this universe, Lily doesn't end up with James Potter. Harry, being from his own universe, arrives in this one and meets Lily. They initially bond over their shared magical abilities and a sense of not quite belonging. As they spend more time together, they develop feelings for each other, which is a huge shock to Harry at first as she is his mother in his own universe.
Another plot idea is that there is a magical bond between Harry and Lily that transcends time. This bond causes them to have shared dreams or visions. Through these, they start to communicate and get to know each other on a deeper level. As they learn more about each other, love begins to develop. This would be a very emotional and complex story as Harry has to grapple with the fact that she is his mother in his normal reality.
One plot idea could be that James and Lily are brought back to life briefly and they meet Harry at a crucial moment in his fight against Voldemort. They offer him words of wisdom and strength that he didn't have before, which gives him an edge in the final battle.
Maybe in the fanfiction, there could be a spell gone wrong that causes Lily to forget her relationship with James and fall in love with Harry instead. Harry, at first, is shocked but then realizes that he has a chance to be with his mother in a different way. The story could then follow their journey of dealing with the confusion and the consequences of this new relationship, including how it affects the prophecy and the fight against Voldemort.
One plot idea could be that Harry discovers a hidden diary or memory of Lily Evans that has something to do with a lemon - scented charm she was working on. This could lead him on a journey to understand more about his mother's magic and her relationship with certain elements in the wizarding world. Maybe the lemon - scented charm has some special power that can help Harry in his fight against the dark forces.
A great fanfiction could be about their courtship. James could write her love letters filled with his thoughts and feelings. Lily would keep these letters hidden away, reading them when she was alone and slowly falling more in love with him through his written words.
One unique plot idea could be that Lily Evans is somehow able to communicate with Harry through a special magical object. For example, a mirror that was enchanted by Lily long ago. This could allow her to give him advice and guidance during his adventures at Hogwarts. Another idea is that Lily's ghost lingers in a way that only Harry can see, and she helps him uncover secrets about the wizarding world that were lost over time.
Another interesting plot could be that they are sent forward in time instead. They have to adapt to the future wizarding world which has changed a great deal. They might be shocked by new magic technologies and different social structures, and their reactions to these changes can make for an engaging story.
There are fanfictions that imagine Lily's life if she had survived. In these stories, she would be a key figure in Harry's life, guiding him and protecting him in ways that Dumbledore or others couldn't. She might also play a role in the wizarding world's politics, using her intelligence and magical abilities to bring about positive change.
A popular fanfic in this category is 'The Untold Story of Lily Evans Potter'. This story focuses on Lily's role in the fight against the Dark Arts during her time. It gives a detailed account of her relationship with James Potter from her perspective, which is really interesting as it often differs from what we can assume from the original books. It's a must - read for any Lily Evans Potter fan.
One great Harry Potter fanfiction involving Harry and Lily Evans is 'The Time - Traveler's Daughter'. It presents an interesting take on how Harry's relationship with his mother could have been explored through time - travel. It has a really engaging plot and the characterizations are well - done.
One idea could be Lily Luna Potter discovers a hidden spellbook that once belonged to Harry Potter. She starts to experiment with the spells inside and accidentally opens a portal to a parallel magical world. There, she meets a younger version of Harry Potter and they have to work together to find a way back home while also facing the new and strange magical threats in that world.