One idea could be an OC who has a special ability to communicate with spirits on a different frequency than the Ghost Adventures crew. For example, they can hear the spirits' true intentions while the crew only picks up on the more surface - level hauntings. This could lead to some tense moments where the OC has to convince the crew of what's really going on.
An OC could be a descendant of a powerful medium. They join the Ghost Adventures crew to learn more about their heritage and also to use their latent powers to help the crew. Their powers might be unpredictable at first, causing some chaos during investigations, but as they gain control, they become an invaluable asset to the team.
One idea could be an oc who is a new student at Acme Looniversity. They could struggle to fit in at first because they have a unique talent that the other toons don't understand, like being able to communicate with inanimate objects. Another plot could involve an oc who accidentally gets involved in a time - traveling adventure with the main Tiny Toon characters and has to help them fix the timeline. Maybe an oc that has a secret power and must keep it hidden from the villains in the Tiny Toon world while also trying to use it for good.
One idea could be that the Ghost Adventures crew goes to Forks to investigate some strange paranormal activities that seem related to the vampires and werewolves in Twilight. Maybe they find out that some of the 'hauntings' are actually caused by the territorial disputes between the two supernatural groups.
One idea could be an OC who is a former Ghost turned rogue and now the Ghosts have to hunt them down. This could add a lot of moral complexity to the story.
One idea could be an OC who is a former criminal turned informant for the Ghosts. They have unique skills from their past life that help the team in unexpected ways. For example, they know all the secret passages in the drug cartel's strongholds because they used to work with some of the lower - level members.
Another interesting crossover could be with Buffy the Vampire Slayer. Picture the Ghost Adventures guys arriving in Sunnydale and working with Buffy to figure out the supernatural happenings there. Maybe they help Buffy with some of the ghosts she has to deal with, while she teaches them a thing or two about combatting the forces of evil.
One idea could be an OC who is a hacker with a unique cybernetic implant that gives them the ability to infiltrate the most secure networks undetected. They could get caught up in a plot that involves both corporate espionage and a deeper conspiracy within the government.
An interesting OC could be a street artist. They have a unique connection to the spirit world through their art. One day, while creating a mural inspired by the Ghost Rider, they are possessed by the spirit and become a new kind of Ghost Rider, using their art to fight evil.
A great plot for Pokemon Adventures fanfiction could be centered around a Pokemon with amnesia. The trainer then tries to help the Pokemon remember its past, which leads them on a journey filled with various challenges and revelations. It could also involve the discovery of a hidden Pokemon society that has its own rules and customs. This would add an element of mystery and exploration to the story. Additionally, a story about a trainer who is able to communicate with Pokemon in a unique way, like through dreams or telepathy, could be really interesting.
Perhaps an OC is a young archaeology student who idolizes Nathan Drake. They manage to get involved in one of his expeditions through sheer determination. Along the way, they learn from Drake and also teach him new things about modern archaeological research methods. It could be a story of growth and adventure for both characters.
One idea could be an OC who is a lightning - style user in Kumogakure and has to face a powerful enemy from another village. The OC could discover a new jutsu during the battle.