Think about it. The Arrow team is all about using technology and their physical skills to fight crime in Star City. When they meet the Winchesters, who are used to dealing with ghosts, demons, and angels, there would be a huge culture shock. Oliver would initially be distrustful of the supernatural elements that the Winchesters bring. But as they face a common enemy, like a demon that is using high - tech gadgets to cause chaos in the city, they would start to work together. Sam would be trying to explain the supernatural aspects to Felicity, who would be fascinated and trying to find a scientific explanation for it all. And Dean would be teaching some of the Arrow team basic self - defense against supernatural threats.
Sam and Oliver would probably start off a bit cautious with each other. Sam, being the more cerebral of the Winchesters, would be interested in Oliver's methods of protecting the city. Oliver, on the other hand, might be a bit skeptical of Sam's supernatural knowledge at first. Dean would likely bond with Diggle over their combat skills. They'd probably exchange stories about their battles, and Dean might even show Diggle some of his unique ways of taking down enemies. Castiel, with his angelic powers, would be a mystery to the 'Arrow' characters. Felicity might be both intrigued and a bit scared of him, but she'd also be eager to understand how his powers work.
If Castiel were to be in this crossover, he would be very confused by the walkers at first. He's used to dealing with demons and angels, not undead creatures. But he would quickly adapt and use his angelic powers to protect the group. Rick from The Walking Dead would see Castiel as a valuable asset but also be a bit wary of his otherworldly nature. They would have to learn to trust each other as they both have the goal of protecting the survivors and finding a way to end the chaos in their respective worlds.
Mabel would be excited to meet the Winchester brothers. She might try to get Dean to tell her all his hunting stories and would probably try to knit them some cool accessories. She could also introduce Sam and Dean to Waddles. Dipper would be a bit more cautious around them at first, but as they started working together, he would respect their skills and knowledge. The characters would need to learn to trust each other quickly since they come from different worlds but are facing similar threats.
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.
The powers of the Supernatural characters, like Sam's psychic abilities and Dean's combat skills, would contrast with the more otherworldly powers of the Good Omens characters. Aziraphale's ability to perform miracles and Crowley's demonic powers would be on a different scale. For example, Sam's psychic visions might be able to predict events that Aziraphale and Crowley are involved in, but they might not fully understand how he gets these visions at first.
A cool plot could be a time - travel crossover. The 'Supernatural' crew travels to a time when Star City was in its early days. They meet a young Oliver Queen and end up changing some events that have a ripple effect on both their universes. This could lead to new alliances and new enemies. Also, a powerful witch from 'Supernatural' could put a spell on Star City that only the combined efforts of the two groups can break.
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 great 'Supernatural' and 'Arrow' crossover fanfiction is 'The Hunt in Starling City'. It combines the dark, supernatural elements of 'Supernatural' with the gritty, urban setting of 'Arrow'. The story has Dean and Sam Winchester arriving in Starling City to hunt a demon that's been causing chaos in the criminal underworld, which draws the attention of Oliver Queen and his team. They initially clash but then realize they need to work together to stop the greater evil.
Oliver Queen and Dean Winchester would be an interesting pairing. Oliver is used to leading a team and taking on tough enemies in his city. Dean is a no - nonsense hunter. They could have some great banter and learn from each other's combat and survival skills.
Gibbs from NCIS would probably be very skeptical of the Supernatural elements at first. He's a man of facts and evidence. But as he sees things that can't be explained, he might start to open up. Dean Winchester, on the other hand, would likely be impatient with the slow - moving NCIS investigation process. They would need to find a middle ground to interact well.
The Flash's super - speed can be really useful in the Supernatural universe. He could quickly move between locations while hunting monsters or escaping dangerous situations. For example, if Sam and Dean are surrounded by demons, the Flash could use his speed to rescue them. On the other hand, the Winchesters' knowledge of the supernatural can help the Flash deal with threats that have a magical or otherworldly origin in his own city.