You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of various fanfictions, including Highlander crossovers. Just use the search function and type in 'Highlander Crossover' to find relevant stories.
Yes, there are likely some interesting ones. You can start by looking on fanfiction websites. Some might explore unique character interactions, like how the characters from Torchwood would interact with the immortals in Highlander. They could create new and exciting storylines that combine the two universes' mythologies.
The uniqueness lies in the combination of two very different universes. NCIS is a modern - day crime - solving show, while Highlander has elements of immortality and a different kind of combat. When crossed over, it can create stories that are full of contrasts and new possibilities.
Yes, there are likely some interesting ones out there. A good place to start looking could be on fanfiction websites like Archive of Our Own. Some might explore how the characters from NCIS interact with those from Highlander in unique crime - solving scenarios or character - development arcs.
There could be a 'forever highlander crossover fanfiction' that pairs the Highlander with the 'Buffy the Vampire Slayer' world. Imagine a Highlander in Sunnydale, facing vampires and demons. His immortality would give him an edge in battles, and his code of honor might clash or align with Buffy's mission. It would be a great mix of two different supernatural concepts.
You can try websites like Archive of Our Own (AO3). It has a vast collection of fanfiction from various fandoms, and there's a good chance you'll find some torchwood highlander crossover stories there.
One idea could be that Buffy and the Highlander team up to fight a common supernatural enemy that is causing chaos in both their worlds. Maybe a powerful demon that can't be killed easily, and the Highlander's immortality and Buffy's slayer skills are needed to defeat it.
A common storyline is the clash of cultures. The military - oriented Stargate teams with their high - tech weapons and strategies meet the lone - wolf immortals of Highlander. There could be a situation where an immortal Highlander is mistaken for an enemy by the Stargate team. Or, the Stargate team might need the help of an immortal to defeat a powerful alien foe that is immune to their normal weapons. The immortals' ability to sense each other could also play an interesting role in a Stargate - Highlander crossover, like when they are on a planet full of hidden threats and the immortal's sense helps the team avoid danger.
You can start by looking on fanfiction.net. It has a large collection of fan - created stories, and there's a good chance you'll find some Highlander SG1 crossovers there.
One interesting story could be about how the characters from Highlander and SG1 team up to fight a common enemy that has the ability to travel between different dimensions. This would bring together the immortality concept from Highlander and the inter - galactic exploration of SG1.