A common one is shipping wars. Fans who supported different character pairings would get into huge arguments. They'd attack each other on social media, which made the fandom environment very toxic. It was really scary for those who just wanted to enjoy the show and the fan creations in peace.
One common plot twist could be the revelation of a character's unexpected heritage. For example, a seemingly ordinary character might turn out to be related to a powerful clan. Another could be the betrayal of a trusted ally. In the Naruto universe, where loyalty is highly valued, this can be a huge shock. And sometimes, a long - dead character might be brought back to life in a very unexpected way, like through some ancient and forgotten jutsu.
Well, often in these fanfics, a major plot twist is the technology or magic system. In the RWBY universe, Dust is important. But in the alternate universe, it could be that Dust has no power, or it has some completely different and unexpected effect. And the semblances of the characters might change drastically. Say, Yang's ability to absorb damage and use it as strength could turn into something like the ability to heal others instead. And then there's the world - building aspect. The alternate universe could be a post - apocalyptic wasteland instead of the somewhat civilized world we see in RWBY, which would be a huge plot twist for the characters to deal with.
In general, there are so many elements in science fiction that it's hard to say if Holt is common. There are classic elements like spaceships, aliens, time travel etc. that are widespread. But if Holt is a unique idea, like a new form of artificial intelligence named Holt in a particular series of science - fiction novels, it's not common across the whole genre. But if Holt is used to symbolize a human's struggle against a technological dystopia which is a common theme, then it could be seen as having some commonality within science - fiction.
I don't think so. Most common elements in adult fanfiction tend to be more mainstream concepts like certain character archetypes or common fictional settings. 'Sidecarangel' sounds very specific and not likely to be a widespread element.
The stick is not a common thing in Daredevil comics. Most of the focus is on Daredevil's other abilities and the villains he faces rather than any specific stick.
Sasuke is often a common character. Since they have such a deep relationship in the original Naruto story, it's likely they'll interact in the alternate universe too. Kakashi could also be a common one. He was Naruto's teacher, so it makes sense for him to be around in different universes. And Sakura, as part of the original team, is also likely to interact with Naruto in these fanfictions.