One interesting Under Cover Twilight fanfiction could be the one where the characters are in a modern-day AU (alternate universe). For example, Bella could be a detective undercover in a case related to the Cullens who are suspected of some mysterious activities. Another might involve a time - travel aspect where a character from the future goes back to the Twilight world undercover to change certain events. There could also be a fanfiction where the vampires are undercover in a human high school not just for the sake of blending in, but for a more complex mission like protecting a secret vampire artifact.
One more option is to follow your favorite Twilight fanfiction authors. If you come across a story you like, see who the author is. Then check if they have written other Under Cover Twilight fanfictions or if they recommend any on their author pages. Additionally, you can look for fanfiction awards related to Twilight. Stories that have won awards or been nominated are likely to be of high quality. This way, you can narrow down your search and find some really great Under Cover Twilight fanfiction.
One idea could be a love triangle. A new character could come to the town in the 'Twilight' world and be drawn to both Edward and Bella while sitting under the apple tree. They might have a unique power that makes the situation even more complicated.
In 'twilight then twilight now fanfiction', there might be alternate timelines. Some stories could show what would have happened if certain events in the original 'Twilight' series had different outcomes. For instance, if Bella had chosen Jacob instead of Edward. This kind of plot twist can make the fanfiction really engaging and offer a fresh perspective on the familiar Twilight universe.
There are fanfictions that focus on the backstories of secondary characters. For example, a story about Rosalie's life before she was turned into a vampire. It might detail her human experiences, her dreams, and how those were shattered when she was changed. This kind of fanfiction can add a whole new dimension to the Twilight universe.
Maybe a fanfiction where the events of 9/11 cause the Twilight world to be more aware of human vulnerability. So, the vampires and werewolves come together to protect humans not just from their own kind but also from future disasters. This could lead to a whole new set of alliances and storylines within the Twilight universe.
One interesting story could be about a different take on Bella's transformation. Maybe she has more control over her new vampire abilities right from the start. Another could be a story that focuses on the friendship between the Cullens and other vampire clans that wasn't explored much in the original. And there might be a fanfiction where Jacob's character has a more complex backstory related to his shape - shifting abilities.
Some family twilight fanfiction might be about the Volturi family. It could show their strict hierarchy and how they maintain order within their family. For example, a story could be about Aro's leadership and how he deals with the different personalities in his family, like Caius' hot - tempered nature. There could also be fanfictions that explore the backstories of the Volturi members and how they came to be part of the family, adding more depth to their characters in the Twilight context.
There are often many stories about a new character being pulled into the Twilight universe. Some might involve the character becoming a part of the vampire - werewolf drama, perhaps befriending Bella or getting caught in the middle of the Cullens' and the Volturi's power struggles.
One interesting twilight wolf fanfiction could be about a wolf with special powers in the Twilight universe. For example, a wolf that can communicate telepathically with all the characters, not just the pack. This would create unique storylines as it could change the way the vampires and wolves interact.
Some Poison Twilight fanfiction could center around a new vampire or werewolf who has a special ability related to poison. Maybe they can use it to protect their territory or as a weapon against their enemies. This would create unique power dynamics and conflicts within the familiar Twilight setting.