Maybe Harry uses some new study methods or has some magical encounters that boost his knowledge and thus gets top owl results. For example, he might discover a hidden spell that helps him remember everything he reads.
Obviously, Harry Potter himself is the central character as the story is about him getting top owl results. Hermione would also be important as she is always the one to help Harry with his studies.
Ron Weasley is another character that frequently shows up. His insecurities about his academic abilities compared to Harry and Hermione can be explored further in relation to the owl results. For example, he might be really disappointed if his results are much worse than his friends', or he could be overjoyed if he manages to do better than expected. And of course, Draco Malfoy can also be a central character. His family's expectations and his own desire to outdo the Gryffindors could be tied into his owl results in interesting ways.
One interesting plot could be that the owl results are mixed up. A student who was expected to do poorly gets top grades and vice versa. This could lead to a whole series of comical and challenging situations as they try to figure out the mix - up and deal with the new expectations.
One possible fanfiction could be about Harry's owl, Hedwig, becoming an Animagus. Maybe she could transform into a human - like form to protect Harry in a dangerous situation. For example, when Death Eaters are closing in on Harry, Hedwig could turn into a wizard - like figure and use magic to fend them off.
One possible fanfiction could be about how Harry Potter's mother's Patronus, which was a doe, had a special connection with an owl. Maybe the owl was a messenger that carried important news related to her protection of Harry. It could be that the owl was charmed to only be visible to her and it played a role in her hiding from Voldemort.
In this fanfiction, perhaps Gaki the owl is a gift to Harry Potter from Hagrid. It could be an owl that is not like the typical owls at Hogwarts. Harry names it Gaki because of its strange behavior. The owl might have a habit of stealing shiny objects from other students, which could lead to some comical situations in the story.
Perhaps in the fanfiction, the owl was a magical anomaly. It was attracted to Lily Potter's pure heart. The owl had the power to transform into a human - like form briefly. Lily discovered this and they formed a pact. The owl - human would protect Harry when she couldn't. So when Voldemort came, the owl - human fought valiantly, but was overpowered. However, it left a magical imprint on Harry that would later help him in his battles.
One unexpected result could be the creation of new and unique magical concepts. Fanfic writers often come up with their own spells or magical creatures that add to the richness of the Harry Potter universe. For example, they might create a spell that combines the properties of two existing spells in a really interesting way.
Another way to make it unique is to set the fanfiction in a different time period within the Harry Potter world. Instead of the main events of the books, it could be set in the past, like during the founding of Hogwarts. The owl Animagus could play a crucial role in the early days of the school, perhaps helping the founders with their magical tasks or being a messenger between different magical communities at that time. This would give a whole new perspective to the story.