In Once Upon a Time fanfiction, a common trope for female OCs is the 'love interest' trope. She could be the love interest of a main character, like Hook or Charming. Then there's the 'mysterious stranger' trope. She arrives in Storybrooke or the Enchanted Forest with a mysterious past and unknown powers. Also, the 'redeemed villain' trope can be applied. Maybe she was once on the wrong side but then sees the error of her ways and joins the good guys in the fight against evil in the Once Upon a Time universe.
One common trope is the 'lost heir' trope. The OC is often revealed to be the heir of some important clan or have a special bloodline. Another is the 'outsider who becomes a hero' trope. They start as an unknown in the Naruto world but through their skills and determination, they rise to prominence. The 'love interest for a main character' trope is also seen a lot, where the OC becomes romantically involved with Naruto or another main character.
One common trope is the 'opposites attract' within the harem. For example, a shy main character surrounded by more outgoing love interests. Another is the 'jealousy' trope, where the members of the harem get jealous of each other's interactions with the main character.
One common trope is the 'New Student' trope. The fem OC arrives at Hogwarts as a new student, often with some mysterious past or special ability that makes her stand out. Another is the 'Love Interest' trope, where she becomes a love interest for one of the main characters, like Harry or Draco. There's also the 'Outcast' trope, where she doesn't fit in with the typical Hogwarts crowd due to her unique views or powers.
A 'found family' trope is quite common. Characters who were alone or estranged in the show form a close - knit family in fanfiction. For instance, Henry might bring together different characters who then become his new family. Also, the 'hurt/comfort' trope, where a character is hurt (physically or emotionally) and another character comforts them, is frequently used in Once upon a Time fanfics.
A prevalent trope is the 'reincarnation' trope. Fans might write about how the characters are reincarnated in different time periods or worlds and how their relationships are rekindled. 'Power - swapping' is another interesting one, where characters exchange their powers and how that affects their relationships and the story. There are also 'secret relationship' tropes, especially for characters who had a lot of chemistry on the show but never got together officially, like Belle and Will Scarlet. Writers create scenarios where they have a secret relationship and all the drama that comes with it.
One popular trope is the 'Mysterious Newcomer'. The female OC shows up out of nowhere, with a strange power or knowledge that intrigues Inuyasha and the gang. Another is the 'Tragic Past' trope. Maybe she lost her family to demons and is now on a journey of revenge. And there's also the 'Love Interest' trope, where she has feelings for Inuyasha or another character in the series.
One common trope is the 'Mysterious Newcomer'. He arrives at Hogwarts and everyone is curious about him. Another is the 'Chosen One' trope, similar to Harry, where he has a special destiny or power. There's also the 'Rebel' trope, where the male OC doesn't follow the normal Hogwarts rules and causes some chaos. For example, he might start a secret club that practices unapproved magic.
One popular trope is the 'Enemies to Lovers'. For example, a hero and a villain character from 'Once Upon a Time' might start off hating each other but gradually fall in love. Another is the 'Soulmate' trope, where two characters are fated to be together, which adds a touch of magic and destiny to the story. And of course, the 'Hidden Relationship' trope is also common, as characters may have to keep their relationship a secret due to the circumstances in the 'Once Upon a Time' universe.
A common trope is the time - travel trope. Maybe a character from Once Upon a Time travels to the Descendants' world in the future or vice versa. Family reunions are also popular, especially when characters from the two shows discover long - lost family connections. And of course, the 'hidden power' trope, where a character discovers a new and unexpected power when they enter the other show's world, which they then have to learn to control.
One popular trope is the 'forbidden love' trope. In 'Once upon a time', there are so many different storybook characters from different worlds and with different statuses, so a relationship between two characters who are not supposed to be together, like a princess and a villain, is quite common in the fanfiction. Another is the 'reunion' trope. Since many characters have lost their memories or been separated in the show, fanfiction often features them reuniting and falling in love all over again.