One possible plot could be that James and Lily have been friends for a long time, but there's always been an underlying tension. One day, after an emotional argument, James can't hold back his feelings anymore and kisses her against the wall.
There could be. A lot of fanfiction explores different romantic or intense moments between characters. 'James kisses Lily against the wall' is a very specific and likely scenario that some fans may have written about. Check the relevant fandom sections on major fanfic sites.
One possible theme could be redemption. Maybe James realizes the wrongs he did to Snape and the kiss is a sign of his attempt to make amends. Another theme could be a change in their relationship dynamics, from enemies to something more complex. For example, a sudden realization of a deeper connection.
One possible plot could be that the portraits of James and Lily are somehow damaged or fading, and Harry has to find a way to restore them. He goes on a quest to find ancient spells or magical artifacts that can help.
One possible plot could be that Leni and Lincoln are in a situation where they accidentally kiss during a game or a prank gone wrong. Then they have to deal with the awkwardness and figure out their feelings towards each other.
One possible plot could be that through some magical time - traveling anomaly, Harry ends up in a different time where he meets Lily before she is with James. They might bond over shared values and a sense of adventure, leading to their marriage. Another plot could involve an alternate universe where the normal relationships are disrupted, and Harry and Lily are brought together by fate to face a great evil together, and in the process, fall in love and marry.
In some versions, James might use his Quidditch skills to create a distraction while rescuing Lily from a dangerous situation Snape unknowingly led her into. For example, he could fly in on his broomstick and snatch her away just as a spell was about to hit her.
One possible plot could be that Voldemort's curse backfires in a different way. Instead of killing them, it transports Lily and James to a parallel magical dimension. In this dimension, they are able to secretly raise Harry while still being alive. They could then use their knowledge of the future to train Harry more effectively and build a stronger resistance against Voldemort. Another plot might involve a powerful magical object that they discover which has the power to protect them from death spells. They could then use this object to not only save themselves but also to help the wizarding world in the fight against the Dark Lord.
One possible plot could be that James, Lily, and Albus travel back in time to the Marauder's era. They could interact with the young versions of their family members, like Sirius and Remus. Maybe they try to change some small events to prevent future tragedies without messing up the timeline too much.
One interesting plot could be Snape seeing Lily and James during a Hogwarts event. Maybe it's a Quidditch match and he watches their interactions. He could be filled with a mix of jealousy and longing as he sees James showing off to Lily. Another plot might involve Snape seeing them in a more private moment in the library. He overhears their conversation about their future plans and it makes him realize how much he has lost. There could also be a plot where Snape has a vision of them through a magical object and it haunts him, making him question his own actions and decisions in relation to Lily.
One challenge could be financial. They might need to figure out how to afford things like baby clothes, a crib, and medical expenses. Another might be emotional stress. Lily could have mood swings during pregnancy, and James might struggle to keep up with her changing emotions.