Another idea is that the Gilmore Girls' world is secretly being influenced by the Supernatural universe all along. The town's quirky characters could actually be hiding their true identities. Miss Patty could be a witch in disguise, using her dance studio as a cover. When the Winchesters arrive, they start to uncover these secrets. Dean might be initially skeptical but soon realizes that there's more to Stars Hollow than meets the eye. Sam would be more open - minded and start researching the town's past, finding connections to other supernatural events across the country.
A plot idea could be Lorelai starting her own business in Stars Hollow. Maybe a small boutique hotel that combines her love for the town and her knack for hospitality. It would be filled with her unique style and charm, and she'd have to deal with all the challenges of running a business, like getting permits and dealing with difficult customers.
Dean Winchester would likely be charmed by Lorelai Gilmore's sass and sense of humor. He might also be a bit protective of her, given his nature. Sam would probably have in - depth conversations with Rory about books and knowledge. Rory, in turn, would be fascinated by Sam's experiences with the supernatural. And Luke would probably be a bit suspicious of the Winchesters at first, thinking they're up to no good in his town.
Another plot could be centered around the town events in 7x08. What if a new character arrives in Stars Hollow during that time? This new character could be a long - lost relative of one of the main characters. They bring with them a mystery about the family's past that shakes up the town and makes everyone re - evaluate their relationships and their place in Stars Hollow.
One idea could be that the Avengers have to deal with a supernatural force that is causing chaos in the city. Maybe it's a powerful demon that they can't defeat with their usual weapons and tactics. They then seek help from the Supernatural world, like Sam and Dean Winchester, who teach them about exorcisms and using holy water.
A cross - over could involve a curse in the 'Arrow' world that has a supernatural origin. Oliver Queen and his team seek the help of Sam and Dean Winchester who are experts in dealing with the supernatural. Along the way, there are clashes in their methods of operation but they gradually learn to trust each other and combine their skills to break the curse.
One idea could be that a supernatural entity from the Supernatural world somehow ends up in Central City and starts causing chaos that only the Flash's speed can help contain. For example, a demon that can possess multiple people at once and the Flash has to use his speed to track down all the possessed bodies before the demon can complete a dark ritual.
One idea could be that Rory, with her love for books and knowledge, ends up in the Stark world and becomes an advisor to the Starks. She could use her quick thinking and education to help them strategize in their political games. Maybe she even teaches some of the younger Starks about the importance of literature and learning, which in turn gives them new perspectives in their world of power struggles.
One idea could be a crossover with 'Doctor Who'. The Doctor and the Winchesters could team up to fight a time - traveling demon. Another could be a crossover with 'Buffy the Vampire Slayer', where Buffy and the boys from Supernatural join forces against a powerful vampire coven that has some sort of connection to the supernatural underworld in both universes. And a crossover with 'The X - Files' would also be cool, with Mulder and Scully investigating a case that turns out to be related to the monsters the Winchesters usually hunt.
A really cool plot might be that the forces of Hell in Supernatural are trying to take over Gravity Falls because of its unique supernatural properties. Sam and Dean, along with Dipper and Mabel, would need to use their combined knowledge and skills. Sam's research abilities and Dean's combat skills, along with Dipper's knowledge of the town's secrets and Mabel's out - of - the - box thinking, to stop the demonic invasion.
One idea could be that Danny and the Winchester brothers team up to fight a ghost that is causing chaos in both the Ghost Zone and the human world. Maybe it's a powerful entity that has the ability to cross between dimensions easily.