A third idea is to cross it with a post - apocalyptic world. The haunted mansion becomes a refuge in a desolate world. However, it has its own set of challenges as the ghosts and spirits within the mansion are not used to the new outside threats. The survivors from the apocalypse have to team up with the mansion's spectral inhabitants to defend against new, more dangerous threats.
One idea could be a story where the characters discover a hidden room in the haunted mansion that holds the key to the mansion's dark past. Another could be about a group of friends who get trapped in the mansion during a storm and start experiencing strange paranormal events. Maybe a story where a character has the ability to communicate with the spirits in the mansion and tries to help them find peace.
One idea could be that the OC discovers a hidden room in the haunted mansion that holds the key to the mansion's dark past. Maybe it was a place where a tragic event occurred long ago. Another could be that the OC has a special ability to communicate with the spirits in the mansion, and they must work together to solve a mystery that has been plaguing the mansion for centuries. For example, a curse that is causing the hauntings.
One interesting plot could be that a group of Pokemon trainers enter the haunted mansion in search of a rare and powerful Pokemon. But once inside, they discover that the Pokemon they're looking for is actually a guardian of the mansion, protecting a dark secret. And they have to face various spooky challenges and ghost - type Pokemon along the way.
A plot could revolve around Luigi having to rescue all the Toads that have been scattered throughout the mansion in different forms - some are invisible, some are trapped in paintings. As he searches for them, he uncovers secrets about the mansion's original owner and their dark past.
Well, perhaps the Harry Potter mansion in the fanfiction could be a place where a secret society of dark wizards once resided. The main characters stumble upon it and find clues about a long - forgotten dark magic plot. Or it could be a mansion that has been enchanted to change its layout constantly, like a magical maze. And it might also be the place where a powerful magical object was created, and now everyone is after it.
One idea could be that the main character starts seeing the ghosts of the vampires' past victims within the Twilight world. These ghosts could be trying to warn the character about some hidden danger related to the vampire clans. Another could be a haunted location in Forks, like an old mansion, that has a connection to the werewolves' history, and the characters have to uncover the mystery.
You could include Sherlock Holmes. His deductive skills would be very useful in trying to figure out the mysteries of the haunted mansion. He could analyze the strange happenings and the behavior of the ghosts and spirits, perhaps even finding a logical explanation for some of the seemingly supernatural events.
One idea could be a crossover with a supernatural detective show. The Hathaways could team up with the detective to solve a mystery that involves both their worlds. Maybe a powerful spirit is causing chaos in both the Hathaways' haunted house and the city where the detective operates.
Maybe an OC that is a ghost hunter from another dimension comes to Luigi's Mansion. This OC has advanced ghost - hunting tools and techniques that Luigi has never seen before. Together, they team up to face an extremely powerful and malevolent ghost that has been terrorizing the mansion for a long time.
One idea could be exploring the backstory of the mansion itself. Maybe it was once a normal house before the spooky events started. Another could be focusing on a particular character's experience inside the mansion, like how they deal with the constant jumpscares. And a third idea might be to create a story where the characters find a way to break the curse of the mansion.