Perhaps a character from the Stargate Atlantis world could have some latent magical abilities. This discovery could lead to them being sent to the Harry Potter world to learn more about magic. In turn, wizards from the Harry Potter world could be intrigued by the technology in Atlantis and travel there to study it.
One idea could be to have the wizards from Harry Potter's world discover the Stargate Atlantis technology. Maybe they could use magic to help repair or understand some of the advanced technology in Atlantis. For example, Hermione could use her vast knowledge of spells and ancient runes to decipher the Atlantis control panels.
Create interesting character interactions. Imagine how Hermione would get along with Dr. Weir. They are both strong female characters but from very different backgrounds. Maybe Hermione would be fascinated by the scientific research in Atlantis and Dr. Weir would be intrigued by magic. You should also think about how the different power dynamics in the two worlds would play out when the characters meet.
There might be a fanfiction where the characters from Harry Potter are somehow transported to the world of Stargate Atlantis. Harry, Hermione, and Ron could find themselves in a completely different environment, having to learn about the Pegasus Galaxy and its threats. Maybe they would use their magical skills to fight off the Wraith. It would be a great story of two different fictional universes colliding and the characters having to adapt to each other's worlds.
Yes, there are likely some fanfics out there that blend the two. Some fans might be intrigued by the idea of Harry Potter characters exploring the lost city of Atlantis, with its own unique magic and secrets. It could involve Harry and his friends on a quest in Atlantis, facing new challenges and perhaps even learning new types of magic.
In a Stargate fanfic about Atlantis Calls and gene members, it could focus on the relationships among these members. They might come from different backgrounds but are united by their genetic traits. There could be rivalries or friendships formed as they are all summoned by Atlantis. Their genes could also be a source of mystery, with some characters not fully understanding the extent of their powers until they are put to the test in the situations presented by Atlantis.
The Stargate characters are used to dealing with advanced technology and alien cultures. When they meet the Harry Potter characters, they might be initially confused by magic. For example, Jack O'Neill might be both amused and intrigued by the spells the wizards cast. Meanwhile, Harry Potter and his friends would be curious about the Stargate technology and the different worlds it can access.
Archive of Our Own (AO3) is also a wonderful resource. It often has well - organized and high - quality fanfics. The tagging system there makes it easy to find exactly what you're looking for, whether it's a specific character - centric story or a certain type of plot.
There are also fanfics that expand on the Atlantis setting itself. They might describe new parts of the city that were not shown in the original series, or create new adventures that take place within the city's unique architecture and technology.
First, know both universes well. For a Stargate Atlantis crossover, you need to understand the technology, characters, and settings of Stargate Atlantis as well as the other universe you're crossing it with. Then, come up with a unique concept. Maybe it's a situation where the Atlantis team has to team up with characters from another show to defeat a common enemy. Keep the characters in - character. If you're writing a crossover with, say, Star Wars, make sure the Atlantis characters act as they would in their own show while interacting with the Star Wars characters.
The magic in Harry Potter could enhance the functionality of the Stargate. For instance, spells could be used to better navigate through the Stargate network or to protect the Stargate from unwanted intruders. Magic could also be used to power the Stargate in a different way than the normal power sources in the Stargate universe.