I really like 'Crossroads of Krypton and the Hunting Life'. In this fanfiction, the writers did an amazing job of bringing in the mythology of Smallville and Supernatural. Dean and Sam Winchester end up in Smallville and get involved with Clark's world. It's full of action and some really cool character moments. It shows how the different powers and skills of the characters from both shows can work together or clash in interesting situations.
The clash of different mythologies. Smallville has its Kryptonian and small - town - hero story, while Supernatural has demons, angels, and hunters. When these two collide in a fanfic, it creates a really unique and exciting world. For example, seeing how Clark's superpowers interact with the magic and weapons of the Winchester brothers.
One idea could be that the Winchesters end up in Smallville while hunting a demon that has some connection to LuthorCorp's experiments. Maybe the demon is using the kryptonite there for its evil deeds. Another could be that Clark Kent discovers the existence of the supernatural world through Sam and Dean. He could initially be skeptical but then realize there are threats that even his powers might not be enough to handle.
Well, a cool plot could be that an ancient, powerful entity from the Supernatural world is awakened in Smallville. Clark discovers it while trying to protect the town. He realizes he can't handle it alone and contacts Bobby Singer through some means. Bobby then sends Sam and Dean to help. They initially have a hard time trusting Clark because of his superpowers, but soon realize they need his help. As they battle the entity, they discover it has ties to an old, forgotten lore that involves both the kryptonite on Earth and a powerful demon they once fought. They have to combine their knowledge and powers to defeat it.
Definitely Clark Kent and Dean Winchester. Dean has his tough - guy hunter persona, while Clark is the all - American good guy with superpowers. Their different approaches to protecting people would make for some great banter and clashes of ideology. Another interesting interaction would be between Sam Winchester and Lex Luthor. Sam's intelligence and his experience with the supernatural could put him at odds with Lex's brilliant but often morally - grey mind. And Castiel and Chloe Sullivan could also have an interesting dynamic. Castiel's otherworldly nature and Chloe's inquisitive journalist side would lead to some really unique conversations.
Definitely Clark Kent and Dean Winchester. Clark with his superpowers and strong moral code, and Dean with his tough - as - nails hunting skills and loyalty. They could have some great banter as they come from such different worlds but find common ground in protecting people. Another interesting pairing could be Sam Winchester and Chloe Sullivan. Sam's intelligence and knowledge of the supernatural could pair well with Chloe's investigative skills.
The ability to reimagine character relationships is also unique. Characters who might not have interacted in their original shows can form new alliances or rivalries in smallville crossover fanfiction. For instance, a character from Smallville could have a completely different relationship with a character from 'Supergirl' in a crossover. This gives fans a chance to see their favorite characters in new lights and explore different emotional arcs.
I really liked a fanfic called 'Power Convergence'. In this story, the Charmed Ones end up in Smallville and they have to figure out how to get back home. Along the way, they meet Clark and his friends. It's a great read because it shows how the different power dynamics from each show would play out when the two worlds collide.
One key element is the character interactions. Seeing characters like Clark Kent and Oliver Queen interact, given their different backgrounds and powers, is really exciting. Another element is the merging of storylines. For example, how the threats in Smallville might be related to those in the Arrowverse.
A common theme is the clash of two different worlds. Smallville is more of a small - town superhero origin story, while Buffy deals with the supernatural in a more urban and 'chosen one' kind of way. So, the fanfics often explore how these two concepts collide.