No, it's not appropriate. Fanfiction should focus on positive aspects such as character development, new adventures, or exploring relationships in a non - explicit way. Sexualizing a character in fanfiction goes against the spirit of most fandoms which are often family - friendly or at least should be respectful of all ages.
Often, baby Killua in fanfiction is presented as having a strong bond with certain characters from an early age. His loyalty and protectiveness, which are traits that are more prominent as he grows older, are sometimes hinted at in his childhood. He can also be quite endearing, with his small - child clumsiness and his determination to learn new things.
You could write about Killua's friendships. For example, his relationship with Gon and how they support each other through their adventures. This would be a positive and in - line - with - the - spirit - of - the - story type of fanfiction.
Adventure is also a common theme. The characters from Killua's world and RWBY's world going on quests together. They might be on a mission to stop a powerful enemy that threatens both their universes. This usually involves a lot of action scenes, battles against unique and powerful foes. And of course, there's often some element of mystery, like trying to figure out the secrets of the other world or the true motives of certain characters in the crossover.
Another theme is friendship. Killua is used to a certain type of friendship from his own story, and when he meets RWBY characters, new bonds are formed. It's about how he adapts to their group dynamic and vice versa. For example, his relationship with Ruby, who is very different from his friends back home.
Adventure is also very common. The OC usually gets involved in Killua's dangerous and exciting world of being a Hunter. They might be on a mission to find a rare item or defeat a powerful enemy. And there's often a theme of trust - building. Killua has to learn to trust the OC and vice versa.
Yes, there are some. You can start by looking on fanfiction websites. Some authors might create stories where they draw parallels between Naruto and Killua, perhaps in terms of their growth, their relationships with friends, or their unique abilities.
The theme of growth is also prevalent. They both start as somewhat naive boys and grow into powerful and more mature individuals. In 'naruto is like killua fanfiction', you might see how they influence each other's growth, for example, Naruto's positive outlook might affect Killua's more cynical view at times, and vice versa.
One popular 'killua and gon fanfiction' is 'A New Adventure'. It takes the two characters on a journey to a mysterious island not shown in the original series. Another great one is 'Bond Strengthened', which focuses on how their friendship deepens during a difficult quest. There's also 'The Hidden Powers' that explores new abilities they might discover.
One common theme is self - discovery. The OC often discovers new things about themselves while being with Killua. Another theme is friendship evolving into something more. For example, they start as friends or allies and then gradually develop romantic feelings. Also, there's the theme of overcoming differences. Since the OC is not from the original story, they usually have different values or abilities than Killua, and they have to overcome these differences to be together.