If we think about it, Hannibal's refined and sophisticated nature would contrast greatly with the rough - and - tumble world of the Winchesters. But in a crossover, he could offer his unique insights into the more psychological aspects of the cases they encounter. For example, when dealing with a possessed person who has a complex backstory, Hannibal could help them understand the human element behind it. Meanwhile, the Winchesters would introduce Hannibal to the world of the supernatural, which would be a new and exciting area for him to explore.
Dean would probably be very suspicious of Hannibal from the start. He's seen a lot of bad guys, and Hannibal's calm and collected demeanor would set off his alarm bells. Sam, on the other hand, might be more interested in understanding Hannibal's motives. Hannibal would likely see the Winchesters as fascinating specimens. He might try to analyze their relationship and use it to his advantage.
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.
On the other hand, Sam and Dean's knowledge of the supernatural would be invaluable to Supergirl. They could teach her about different types of demons, how to detect them, and what weaknesses they have. Their skills in using various weapons like the Colt or salt - loaded shotguns could be combined with Supergirl's powers. For instance, Dean could shoot a salt - loaded shotgun at a group of demons while Supergirl uses her super breath to blow the salt towards a wider area, maximizing the effect.
Bill Cipher would be a major wildcard in their interactions. If he were to cross paths with the Winchesters, he would likely try to manipulate them for his own amusement. He might offer them false information or try to pit them against the other characters in Gravity Falls. The Winchesters, being used to dealing with devious creatures, would have to be on their guard and figure out a way to outwit Bill while also trying to solve whatever mystery has brought them to Gravity Falls in the first place.
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.
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.
The characters would likely have a mix of admiration and friendly rivalry. For example, the cool and collected protagonist of Persona 5 might be intrigued by the more laid - back nature of the Persona 4 protagonist. Meanwhile, the Persona 3 protagonist, with his more somber and serious demeanor, could initially seem a bit intimidating to the others. But as they get to know each other, they would start to bond over their shared experiences of fighting Shadows and protecting their worlds.
The 1987 Turtles would probably be very curious about the more serious and intense 2003 Turtles. They might crack jokes at first to ease the tension, while the 2003 Turtles could be a bit annoyed by their silliness. But as they face challenges together, they'd start to respect each other. For example, when fighting Foot Soldiers, the 1987 Turtles' acrobatic and fun - loving fighting style could complement the 2003 Turtles' more strategic and brutal combat.
In terms of magic, the witches in 'True Blood' have their own brand of magic which is different from the magic and spells we see in 'Supernatural'. If they were to interact, there could be some unexpected results. Maybe a spell from a 'True Blood' witch could enhance the power of a weapon used by the Winchesters. Or a spell from 'Supernatural' could backfire when used in the world of 'True Blood' due to the different magical rules in each universe. This could lead to some comical or dangerous situations as the characters try to figure out how to work together.
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.