Well, you could focus on the relationships between the characters. Since it's a 'year in a day', there's a lot of potential for fast - paced relationship development. Maybe two characters start as enemies in the 'morning' but by 'evening' they've fallen in love. Or perhaps a character has to deal with the loss of a loved one within this compressed time frame and how they cope with that grief.
One idea could be an OC who is a brilliant scientist that discovers a new weakness in the alien technology just in time for the Independence Day battle. Another could be an OC who is a pilot from a small town and has to step up and fight the aliens, bringing a sense of hometown heroism to the story. Maybe an OC who is a diplomat trying to negotiate with other countries during the alien invasion to unite the Earth's defenses more effectively.
One idea could be that the OC is a long - lost relative of one of the main characters in 'knight and day'. They show up unexpectedly and have some special skills or knowledge that helps in the adventure. For example, they might be an expert in a certain type of martial art that is useful against the villains.
A really unique plot could be Naruto living the same day as the day Sasuke leaves the village. He could keep trying different things to stop Sasuke. Some days he might try to talk to Sasuke more about their friendship, other days he could try to prevent Orochimaru's influence from reaching Sasuke, which would be a very emotional and character - driven story.
Well, a great plot could involve a year - long competition in the Sakura world. Different characters compete in various challenges throughout the year, and there are a lot of ups and downs. There could also be a plot where a character has to endure a year of hardships away from Sakura but is constantly thinking about her. Or perhaps a story where a new character arrives in the Sakura - filled world and spends a year learning about its unique culture and traditions.
One idea could be a modern Cinderella story where she is a struggling artist instead of a maid. The prince could be a famous art collector who discovers her work at a local gallery. Another could be a Snow White retelling where the seven dwarfs are a group of misfit hackers who protect her from the evil queen's cyber - attacks. And a third could be a Beauty and the Beast story set in a high - tech research facility where the 'beast' is a scientist with a disfiguring accident and 'beauty' is a young intern who helps him regain his confidence and reverse the damage.
Well, perhaps on Prince Day, there could be a competition among the princes of different lands. The winner gets a magical artifact. Prince Bubblegum enters, but he has to face some tough opponents. And then there's the idea of a prince who has lost his memory on Prince Day and Finn and Jake have to help him remember who he is and where he's from. Or a story where a prince's secret power is revealed only on Prince Day, and it causes chaos until he learns to control it.
Perhaps the heroes discover a plot by a super - villain to use the patriotic fervor of Independence Day to his advantage. He plans to brainwash the population using a mind - controlling device disguised as a fireworks display. The young justice team has to figure out how to stop this without ruining the holiday spirit for everyone.
One plot idea could be that Harry wakes up on the same day of the Battle of Hogwarts every time. He has to keep reliving the day, trying different strategies each time to minimize the casualties. This would add a new layer of depth to the already intense battle and show his growth as a wizard and a leader with each repetition.
Another plot could involve Elena dealing with a family crisis. For example, a family member gets sick and she has to take on more responsibilities while also taking care of herself, day by day. She could learn about the importance of family and self - care during this process.
Perhaps in the fanfiction, we could see a different side of the foreign students. Like, the Beauxbatons and Durmstrang students could have their own hidden agendas. One of them might be in love with Harry and tries to protect him during the tournament tasks. This would create a whole new dynamic of relationships and loyalties within the story.