A more complex plot might be that there are multiple groups trying to control the invisibility power. The main characters in the fanfiction get caught in the middle of this power struggle. They have to decide which side to support while also dealing with the challenges of being invisible, like not being able to touch things without revealing themselves.
One plot idea could be that the characters discover the invisibility power has a time limit and they have to complete a mission before they become visible again. For example, they need to retrieve a stolen artifact from a heavily guarded place.
A simple plot could be that the reader is a student at a school where Slappy has been accidentally brought to life. The reader has to figure out how to stop Slappy from causing chaos in the school before it's too late. Maybe they find an old book in the library that has the key to putting Slappy back to sleep.
One plot idea could be that Ray and Amanda discover a haunted lemon orchard. In the orchard, the lemons seem to have a strange power that causes goosebumps on anyone who gets too close. They have to figure out the mystery behind it, like if there's an old curse or some kind of supernatural entity attached to the orchard. Maybe they find an old diary hidden among the lemon trees that gives them clues.
One idea could be to create a new adventure for the main characters in a different spooky setting, like an abandoned amusement park. Another is to write about a crossover between Goosebumps and another popular horror series. Maybe the Goosebumps monsters team up with some classic horror movie monsters.
One idea could be a story where the main character discovers that the vampire breath has a special power. For example, it can freeze time for a short period, and they use this to their advantage to outwit the vampires.
One idea could be that the characters discover a magical object that makes them invisible. They then use this new - found power to solve mysteries in their town, like finding out who has been stealing from the local shops at night. They follow the thieves without being detected and finally expose them, becoming local heroes.
One idea could be that Snape's invisible friend turns out to be a manifestation of his repressed childhood self. It could help him face his past traumas and insecurities.
A popular choice could be a girl named Lily. She is curious and brave. When she becomes invisible, she decides to explore the secrets of her town that no one else has been able to. She might find out that there are some spooky things going on underground.
A great plot for a social invisible OC in Naruto fanfiction could be that they have a unique chakra ability that is both a blessing and a curse. It makes them stand out in a way they don't want, so they try to hide it. However, a powerful enemy discovers their secret and tries to use them for their own evil purposes. The OC then has to decide whether to keep hiding or use their power to fight back. Or, the OC could be a historian of the ninja world, but because they are so quiet and unassuming, no one realizes they hold the key to an ancient prophecy that could save the village from destruction.
One idea could be exploring Addie's encounters with different historical figures in more depth. For example, how she influenced or was influenced by them during specific events. Another could be a story where she tries to find a way to reverse her curse in a new and unexpected way, perhaps with the help of a modern-day character who has some unique knowledge or ability.
One possible plot could be that they meet during a multiverse - related event. Maybe the Invisible Woman's powers get affected by some strange energy during a battle, and Peter Parker, with his spider - sense, is the only one who can detect her even when she's invisible. This leads to them getting closer and eventually falling in love and getting married.