What are some interesting Buffy Highlander crossover fanfiction ideas?

Well, perhaps there's a Highlander who stumbles into the wizarding world. He might be confused at first by all the magic but then realizes he can use his immortality and combat skills to his advantage. He could get involved in the fight against Voldemort, using his unique abilities. Or, there could be a magical tournament in the Harry Potter world that also includes Immortals from the Highlander world, and they compete using both magic and their Highlander powers.

One idea could be a Highlander character finding a Stargate and being transported to different planets. They could use their immortality to survive in the various dangerous situations on alien worlds and perhaps encounter Goa'uld who are interested in their immortality.

One idea could be that Xander discovers he has the immortality of a Highlander. He then has to navigate his newfound ability while still dealing with the usual supernatural threats in his world. Maybe he teams up with a Highlander character to learn more about his new condition.

One idea could be that Buffy and the Scooby Gang find themselves in Forks and have to deal with the vampire situation there. They might initially clash with the Cullens due to different ways of handling vampires. Another could be a love triangle between Buffy, Edward, and Angel. It would add a new layer of complexity to the relationships already present in both series.

Here's an idea. Buffy and Xander end up in Lothlórien. The elves are initially suspicious but then realize they are there to help. Buffy could use her agility and strength to assist in defending the forest. In another scenario, the Nazgûl could cross over to Buffy's Sunnydale. This would be a huge threat, and Buffy would have to use her knowledge of fighting demons along with the help of her friends and the weapons of Middle - earth (if they can get them) to defeat these powerful enemies.

Another concept could be that a powerful demon from Buffy's world is attracted to the unique vampires in Forks. This demon starts causing chaos, and Buffy and the Cullens have to team up to stop it. During this time, they learn from each other's fighting styles and supernatural knowledge. For example, the Cullens could teach Buffy more about their kind of vampire lore, while Buffy could show them some of her combat techniques against demons.

A possible plot could involve an immortal villain from the Highlander world using the Stargate network to spread chaos across different planets. The SG1 team, with the help of some friendly Highlander characters, has to track him down and stop him before he causes too much destruction.

One idea could be that the vampires in Buffy's world somehow cross over to the Dark Angel universe and the transgenic characters have to deal with them. They might initially mistake vampires for some new kind of transgenic experiment gone wrong. Another idea is that Buffy herself travels to the Dark Angel world and teams up with Max to fight against a common enemy that is threatening both of their worlds, like a powerful demon that has found a way to use transgenic technology for evil purposes.

One idea could be that Buffy and the Bones team have to work together to solve a mystery involving a supernatural entity that leaves behind skeletal remains with strange markings. The Bones team's scientific expertise and Buffy's knowledge of the supernatural would create an interesting dynamic.

Perhaps a spell gone wrong in the Buffy universe causes some of the main characters from there to swap bodies with characters from The Vampire Diaries. This could lead to humorous and tense situations as they try to figure out how to reverse the spell while still dealing with the threats in each other's worlds.