Often, you'll find crossovers where characters from both universes meet and interact. Time travel and exploration of strange new worlds are common themes too.
Common elements in such fanfiction include characters from both shows facing off against mutual enemies or working together on joint missions. Also, the exploration of alternate timelines and the impact of one universe's technology on the other are popular.
One common theme is time travel. Both franchises deal with it, so it often shows up in fanfiction. Another is exploration of new worlds and species.
Often, fanfiction explores the characters' meeting in alternate realities or during major events. Also, there's a lot of focus on how their technologies and abilities combine to solve problems.
His struggle with the ethical dilemmas of medical practice in space is also a common theme. Since he has to deal with different alien physiologies, he often faces tough decisions. In some fanfictions, this is shown through his internal monologues as he tries to figure out the best course of action.
A frequent theme is the exploration of different cultures. Since Star Trek is all about encountering diverse alien species, in 'Star Trek and Reader' fanfiction, the reader gets to experience and interact with these cultures. Also, there's the theme of self - discovery. The reader character may grow and learn about themselves while being part of the Star Trek universe, facing challenges and making choices that shape who they become.
Conflict, both internal and external, is also a frequent theme. It could be conflict between different species, or internal struggles within the crew. For example, moral dilemmas are often explored, like whether to interfere with the development of a primitive civilization or not. And of course, the theme of friendship and teamwork is also prevalent. The characters on the Andromeda rely on each other to overcome challenges.
One common theme is McCoy's friendship with Kirk and Spock. Many fanfictions explore how their relationships develop further in different scenarios. Another theme is McCoy's medical skills and how he uses them in challenging situations. For example, dealing with new alien diseases or treating injured crew members during dangerous missions.
Love and romance can be a theme too. Maybe a relationship with another crew member or someone from a different planet he meets during his travels. Additionally, there are themes related to his Russian heritage, like how it influences his thinking and actions on the ship.
One common theme is the clash of cultures. NSYNC comes from a very different cultural background (90s pop music scene) compared to the Star Trek universe. So, fanfictions often explore how they interact with the more science - fiction - oriented and often more serious Star Trek characters.
One common theme is forbidden love. Given the diverse species and different cultures in the Star Trek universe, relationships that are not allowed or frowned upon are often explored. For example, a relationship between a Federation officer and a Romulan.
Another theme is power and its use. In Naruto, there are powerful ninjutsu and kekkei genkai. In Star Trek, there are advanced weapons and technologies. Fanfiction may explore how these different forms of power interact when the two universes collide. For example, could Naruto's Rasengan be enhanced by Star Trek technology? Or could a Star Trek phaser be modified with ninja knowledge? It's all about the combination of the two power systems.