You can start by creating shared experiences. For example, they could be paired up for a mission where they have to rely on each other to succeed. This builds trust. Another way is through misunderstandings. Maybe the OC does something that Miss Martian misinterprets, and they have to work through it to understand each other better. This adds depth to their relationship.
A possible plot is that the OC is a new recruit to the Young Justice team. Miss Martian is assigned to train the OC. At first, they don't get along because the OC is headstrong and doesn't like taking orders. But as they face various challenges together, like fighting against a powerful enemy that targets the team's weaknesses, they start to understand each other better. The OC could also have a secret past that Miss Martian helps uncover, which deepens their bond.
There's also a fanfic called 'Miss Martian's New Path'. In this one, she has to face a new enemy that targets her specifically because of her Martian heritage. It's full of action and also some really touching moments as she leans on her friends in the Young Justice team for support.
In my opinion, the fanfictions that focus on their friendship turning into a romantic relationship are some of the best. It's interesting to see how they navigate their feelings for each other while still being part of the Young Justice team. They both have such different personalities - Superboy being more brash and Miss Martian being more empathetic. When these two personalities interact in a romantic context, it can create a lot of drama and sweet moments. Also, fanfictions that show them training together and growing in their powers side by side are really cool.
Another common theme is her powers. Writers love to create scenarios where she has to use her telepathy or shape - shifting in unique ways. Some fanfictions have her using her powers to solve mysteries within the Young Justice universe. It adds an interesting layer to the stories.
First, do your research on the Young Justice universe, especially about Martians. Know their powers, culture, and how they interact with other characters in the show. Then, create a well - developed OC. Give them a unique personality, backstory, and goals. For example, your Martian OC could have a conflict between their Martian heritage and their new life on Earth.
One interesting fanfiction could be about Superboy and Miss Martian going on a secret mission together. They might face challenges that test their relationship and powers. For example, they could be in a situation where they have to rely on each other's unique abilities to survive.
Superboy would be devastated. He has a special bond with Miss Martian, and her death would likely make him go into a rage. He might start lashing out at the enemy without thinking, blaming them for her death. Aqualad, as the leader, would feel a great sense of guilt. He would question his leadership and decisions that led to the situation. He might become more withdrawn and overly cautious in future missions.
Well, Tumblr can be a great place too. There are many Young Justice fanfic communities on Tumblr. You can search for tags like 'Young Justice Martian OC' and you'll likely find some great fanfictions shared by fans. Some fans also post links to their works on Twitter, so it's worth checking out the #YoungJustice hashtag as well.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of fan - made stories, and you can simply search for 'oc x miss martian' in the search bar. There are likely to be many results there.