Maybe you insert yourself as a nurse in the military hospital where Steve Rogers first became Captain America. You witness his transformation and are one of the first people he interacts with as the new hero. You then become his confidant, and he trusts you with secrets. You might also be involved in helping him adjust to his new role, all while falling in love with his noble and selfless nature.
One idea could be inserting yourself as a new recruit in the Howling Commandos. You could have a special skill, like being an expert in decoding enemy messages. Then, you get to interact with Captain America and the team, facing challenges together and forging strong friendships. Another plot could be that you are a scientist in the same era as Steve Rogers. You accidentally discover a new element that could enhance the super - soldier serum. This draws the attention of both Captain America and the bad guys, leading to a race to protect or steal your discovery.
Your self - insert could be a transfer student from another kingdom with a completely different fighting style. This would lead to interesting interactions with the main characters as they learn from each other. They might introduce new weapons or combat techniques that the others haven't seen before.
A possible plot is that the self - inserted character has to deal with the Omnitrix malfunctioning. This could lead to unexpected and sometimes comical transformations. They might transform into a really weak alien in the middle of a battle or into an alien that is completely inappropriate for the situation, like a tiny alien when they need to be strong. As they try to fix the Omnitrix, they learn more about its inner workings.
You could insert yourself as a human knight. Picture this: you are part of the Stormwind army, and you get involved in the fight against the orcs. During a battle, you find a mysterious artifact that gives you special abilities. This leads you on a quest to find out more about the artifact's origin and how it can be used to save humanity from various threats like the Scourge or the demons.
One plot idea could be an OC who is a scientist during World War II and teams up with Captain America. They could work on some top - secret projects together. Another is an OC who is a foreign agent sent to assess Captain America's abilities and ends up becoming his ally. Maybe an OC from the future who travels back in time to help Captain America prevent a major catastrophe that wasn't in the original timeline.
Another idea is that there's a villain who can manipulate time and space. He sends Captain America to the Naruto world during a crucial time in Naruto's story, like right before a big battle. Captain America's leadership and battle experience help Naruto and his friends come up with a better strategy. And in the process, they learn from each other's values and fighting styles.
One idea could be that you insert yourself as a skilled navigator who joins the Straw Hat crew and forms a special bond with Nami. You could help her create new and more accurate maps, and together face the challenges of navigating through uncharted waters. Another plot could involve you having a special power related to weather control, which complements Nami's own abilities with the Clima - Tact. You work together to protect the crew from powerful storms and enemies that use weather - based attacks.
One idea could be that your self - insert character is a new student at the Yokai Academy. They initially struggle to fit in among the various supernatural beings but gradually discover a unique power within themselves that helps them gain respect. For example, they might have the ability to communicate with spirits that others can't, which becomes useful in solving a mystery at the school.
One idea could be that you insert yourself as a new apprentice to Doctor Strange. You could start with little magical knowledge and learn from him, facing challenges like protecting the Sanctum Santorum from minor demons. Another could be that you are inserted into the story during the time when Strange is facing a powerful enemy and your unique modern - world knowledge helps him in an unexpected way, like using technology to enhance a spell.
How about being a foreign diplomat from Essos? You come to Westeros with the intention of forging trade deals but end up getting involved in the power play for the throne. You could introduce new customs and ideas from Essos, and also have to deal with the xenophobia that exists in Westeros while trying to achieve your own goals.
One idea could be that the self - insert character has a special ability to communicate with Grimm on an empathetic level. This could lead to some really unique storylines where they try to understand the Grimm's motives rather than just fighting them. For example, they might discover that some Grimm are being controlled by a greater, more sinister force, and they have to figure out how to break that control.