One popular theme is the relationships between the different characters from 'Descendants' and how they might interact with characters from 'Once upon a time'. For example, how Mal from 'Descendants' would get along with Snow White from 'Once upon a time'.
Redemption arcs are also quite common. Fans might write about how a character from 'Descendants' who was once a villain, like Evie, could find a new path in a world influenced by 'Once upon a time'. It could involve self - discovery and changing for the better. Also, love stories between characters from the two universes are popular. For instance, a love story between a prince from 'Once upon a time' and a VK (Villain Kid) from 'Descendants'.
In 'Descendants' fanfiction, a common theme is the integration of the villains' kids into Auradon. It's about how they adapt to a new life. For 'Once Upon a Time', time - travel and alternate universes are quite popular. For example, stories where characters go back in time to change certain events in the fairy - tale world.
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.
Family relationships are a big theme. Some fanfics focus on the family dynamics between characters like the Charmings and their descendants. There are also fanfictions that revolve around the theme of identity. Characters in 'Once upon a time' often have complex identities, and fan writers like to dig deeper into how these identities are formed and how they can change over time.
One common theme is time -travel. Since both shows deal with different timelines in some way, fanfictions often explore more about time -travel and how it affects the characters. For example, a character might go back in time to change a crucial event.
One popular theme is alternate universes. For example, what if Emma Swan had grown up in the Enchanted Forest instead of our world. Another theme is exploring different relationships between characters. Some fanfictions focus on a deeper friendship between Regina and Snow White that might have developed under different circumstances. And then there are those that delve into the backstories of minor characters, like how the Blue Fairy came to be.
Redemption arcs are also quite popular. Given that many of the characters in 'Once upon a time' have complex backstories and have done bad things in the past, fans often write about their journey towards redemption. Family relationships are a big theme too. There are stories exploring the bonds between parents and children, siblings, etc., like the relationship between Snow White and her daughter.
One popular trope is the fish - out - of - water. When the Descendants characters are brought into the Once Upon a Time world, they're like fish out of water. For example, the VKs (Villain Kids) from Descendants are used to the Isle of the Lost, and in Storybrooke or other OUAT settings, they have to adapt to a whole new set of rules and cultures. Another is the family connection trope. Since both shows have characters based on fairy tales, finding out new family relations between the two universes is a common and interesting trope. For instance, if a Descendants character is related to an OUAT character in a way not explored in the original shows.
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.
You can try fanfiction websites like Wattpad or Archive of Our Own. There are usually a lot of fanfictions about 'Descendants' on these platforms.
One popular theme is Ruby's relationships. For example, her friendship with Snow White or her romantic relationships within the story's universe. Writers often explore how these relationships develop and change over time.