Maybe there's a plot where Luna Lemons is a magical item that only Lincoln can use to save their town from a mysterious force. They go on an adventure together, facing challenges and growing closer as they do so. In the process, they learn more about each other's strengths and weaknesses.
One idea could be that Lincoln and Luna team up to start a music project. Lincoln discovers he has a hidden talent for writing lyrics and Luna helps him bring those lyrics to life with her music skills.
In this type of fanfiction, a possible plot could be that the pregnancy is unexpected and throws everyone in the harem into a state of chaos. Lincoln Loud then has to step up and become more responsible. He might start learning about parenting, and at the same time, try to keep the relationships in the harem harmonious. There could be sub - plots like some characters in the harem having different ideas about how to raise the child, leading to conflicts that need to be resolved.
Maybe there's a lemonade stand story where Lincoln and the Loud sisters set up a lemonade stand. But they accidentally use some strange lemons that give people who drink the lemonade unique superpowers for a short time. This causes chaos and hilarity in the neighborhood as they try to manage the situation and figure out how to reverse the effects. And they also learn about responsibility and working as a team.
I'm not sure about specific Lincoln x Luna Lemons fanfiction. You could try searching on popular fanfiction websites like Archive of Our Own or FanFiction.net. There might be some unique and interesting stories there.
One idea could be Lincoln getting involved in a mystery at his school. Maybe some important items go missing and he uses his wits to solve it. Another could be a story where Lincoln discovers a hidden talent within his family that no one knew about before. For example, he might find out that one of his sisters has an amazing musical talent that she's been too shy to show, and he helps her gain confidence to perform.
The oc could be a young warrior who is on a quest to retrieve a powerful artifact that Sesshomaru also has his eyes on. Instead of fighting over it, they end up teaming up to face the greater evil that is also after the artifact. This could lead to some really interesting character dynamics as they learn from each other's fighting styles and ways of thinking.
One possible plot could be that they are in a school play together. During a rehearsal, they have a moment where they accidentally kiss. This unexpected kiss makes them both feel a bit flustered and confused. They start to wonder if there are deeper feelings between them, but they're also worried about how their family and friends will react.
One idea could be Lincoln using his physical strength while shirtless to fend off the vampires in a more primal way. Maybe he has some special mark on his bare chest that gives him an advantage against the vampires.
One idea could be that they face challenges from their different clans while being pregnant. Their baby could be seen as a symbol of unity or a threat. Another could be that they go on a journey to find a safe place for their child to be born, encountering various adventures and new friends along the way.
One idea could be that Lincoln discovers a hidden vampire lair beneath the White House. He has to battle the ancient vampires there while also trying to keep his vampire - slaying activities a secret from his political allies.