One common theme is the clash of different cultures. In SG - 1, there are various alien cultures, and in NCIS, there's the military and law - enforcement culture. When they cross over, seeing how these cultures interact is a big part of the story. For example, how the NCIS agents react to the advanced technology and strange alien customs from SG - 1.
Well, in a Stargate SG1 and NCIS crossover fanfiction, there could be a situation where an alien artifact is found at a crime scene that NCIS is investigating. The SG1 team is then called in to figure out what it is. Daniel Jackson could start rambling about the historical and alien significance of the artifact, while Abby from NCIS is trying to analyze it from a forensic perspective. It would be a great mix of science - fiction and crime - solving elements.
One interesting story could be about the characters from NCIS and SG - 1 teaming up to solve a mystery that involves both Earth - based crimes and alien technology. Maybe they have to track down a stolen alien weapon that is being sold on the black market on Earth.
If we consider a crossover, the NCIS characters would be in awe of the technology the SG1 team uses. Ziva would be interested in learning some of Sam's self - defense moves. And McGee would be like a kid in a candy store around all the alien tech. On the other hand, the SG1 team would have to adjust to NCIS' strict protocol. For example, Jack might find it a bit stifling at first, but he'd also see the value in it. The interactions would be full of cultural clashes and mutual learning experiences.
One popular sg 1 ncis crossover fanfiction is 'The Stargate - NCIS Connection'. It combines the unique elements of both shows really well. The characters from SG - 1 interact with those from NCIS in a very engaging way, and the plot often involves solving mysteries that are related to both the Stargate and NCIS universes.
Archive of Our Own (AO3) also has a good selection. It has a tagging system that makes it easy to find specific types of crossovers. You can look for tags like 'ncis sg1 crossover' and also narrow it down by other factors like the rating of the story or the relationships it focuses on.
The characters would interact in very interesting ways. For instance, Jack O'Neill from Stargate SG1 is a military man with a sarcastic sense of humor. He would probably find Gibbs from NCIS to be a kindred spirit in terms of military discipline, but their leadership styles might clash at times. Gibbs is more about leading by example and getting his hands dirty in investigations, while O'Neill has to deal with leading a team on dangerous off - world missions.
One of the most interesting storylines could be a situation where the technology from Stargate SG1 somehow finds its way into the NCIS world. For example, a Goa'uld symbiote might be discovered during an NCIS investigation on a military base. The NCIS agents, being used to normal criminal investigations, would be completely out of their depth dealing with alien technology and the threat of a parasitic alien life form. This would force them to team up with the Stargate SG1 team who have the expertise in dealing with such threats.
One great 'NCIS LA and NCIS Crossover Fanfiction' is 'The Joint Operation'. It combines the unique characters from both shows really well. The plot usually involves a case that requires the expertise of both teams. It shows how the agents from NCIS and NCIS LA interact, like how Gibbs' no - nonsense approach clashes and also gels with Hetty's more mysterious style of leadership.
One common theme is the cooperation between the two teams. Since they come from different but related agencies, the fanfictions often focus on how they learn to work together. For example, they might have to overcome differences in their investigative techniques.