A possible plot could be that Lincoln is kidnapped by a mysterious figure who has a vendetta against the Loud family. The kidnapper takes Lincoln to a remote location. Lincoln, being the brave character he is, tries to figure out the kidnapper's motives while also looking for an opportunity to escape. Meanwhile, his sisters and parents are following every lead they can find, from Lincoln's friends to any strange activity in town. The fanfiction could build up the tension as Lincoln tries to outwit the kidnapper and his family races against time to find him.
Perhaps in this fanfiction, Lincoln is kidnapped by an alien who is fascinated by human behavior. The alien takes Lincoln to their spaceship. Lincoln is initially scared but then starts to learn about the alien's culture. His sisters, on Earth, figure out something is wrong and start looking for clues. Eventually, they manage to communicate with the alien and get Lincoln back.
Maybe it's a new villain in Royal Woods. This person could be jealous of Lincoln's leadership skills within his friend group. So, they kidnap him to try and undermine his confidence and make his friends turn against him. They believe that without Lincoln, the group will fall apart and they can take over as the new 'leader' in the neighborhood.
It could be an angry neighbor who has always been annoyed by the Loud family's chaos. They see Lincoln as the main troublemaker (even if he isn't) and decide to kidnap him to teach the family a lesson.
Perhaps the fanfiction focuses on how Lincoln gets braces and it changes his appearance. His crush could either like the new look or be put off by it at first. He then has to deal with his feelings of insecurity while also trying to show that he's still the same Lincoln, braces or not. For example, he might still be the one to come up with great plans for family outings or helping his siblings with their problems.
Maybe in the fanfiction, Lincoln's bad luck is centered around his hobbies. He loves comic books and wants to start his own collection. However, every time he finds a rare comic he can afford, someone else buys it just before him. Or when he tries to go to a comic convention, his bad luck strikes again and he misses the bus, then gets lost on the way there. His bad luck becomes a major obstacle in his pursuit of his passion.
Maybe it could be about Lincoln getting into a fight with some bullies at school who beat him up because he stands up for someone. Then his family might find out and there's a whole drama about dealing with the bullies and helping Lincoln recover.
One possible plot could be that the sisters accidentally hurt Lincoln during a wild game at home. Maybe they were playing a rough version of tag and pushed him too hard, causing him to get a minor injury like a sprained ankle. Then they feel really guilty and try to make it up to him by doing all his chores for a week.
Perhaps the fanfiction could center around Lincoln getting a special Pokemon that no one has ever seen before. This Pokemon could have some kind of connection to his family back in 'The Loud House'. He then has to protect this Pokemon from various villains in the Pokemon world who want to use its power for evil. Along the way, he makes new friends and has all kinds of adventures.
Perhaps the fanfiction involves Sid being a new neighbor in the Loud House neighborhood. She meets Lincoln, and they start a club together. They face challenges like getting other kids to join and dealing with a bully who wants to shut down their club. This could lead to a lot of fun adventures and them learning about friendship along the way.
They could find a mysterious lemon tree in their backyard that has some sort of magical property. Lincoln and Lori have to figure out what it is and how to protect it from a neighbor who wants to cut it down. As they work together to solve this mystery, they rely on each other's strengths and grow closer as siblings, all while the lemons from the tree play an important role in the story.