Well, they could be part of a mystery where strange things are happening around Elmore. Gumball, with his typical comical and curious nature, teams up with Carrie. They start to investigate and find out that it's related to an ancient curse. Along the way, they learn more about each other's worlds and grow closer as friends while trying to break the curse.
One idea could be an OC who has the ability to time - travel and they use it to prevent a major disaster in Elmore. Another could be an OC that is a new student at school and has a unique power that challenges the status quo among the main characters. Maybe an OC that is a magical creature trying to blend in with the normal residents of Elmore.
A crossover with 'Steven Universe' would also be cool. Gumball and Steven could bond over their unique family situations. They could have to use the power of friendship, Gumball's wacky schemes, and Steven's gem powers to defeat a common enemy, like an evil gem who wants to turn Elmore into a gem colony.
One idea could be that Gumball and his friends find a way to communicate with the zombies and try to co - exist. Maybe they discover that the zombies are not as mindless as they seem and have their own stories.
Maybe Gumball accidentally gets involved in one of Carrie's ghostly family traditions. It could be a ceremony that's full of mystery and he has to learn the ropes quickly to not cause any trouble. He might make some hilarious mistakes along the way, but in the end, it brings them closer.
The Void could be a place where time doesn't exist in the normal sense. Gumball and his family get separated and they each experience different slices of time from Elmore's past, present, and future. They must reunite and figure out how to escape this time - warped Void.
One idea could be Gumball and Carrie going on a magical adventure through different dimensions in Elmore. Maybe they accidentally open a portal while exploring an old abandoned house and end up in a world where the laws of physics are completely different. Another plot could involve them working together to solve a mystery in school, like why some students' memories are being erased.
Their relationship could start off as a bit of a cautious friendship. Gumball might be a bit wary of Carrie's spooky side at first, but as they spend more time together, he realizes she's really kind. And Carrie could see Gumball's fun - loving and adventurous spirit and be drawn to it. Eventually, they become really close friends who support each other through all kinds of crazy situations in Elmore.
A lemon fanfic could also focus on a character's backstory that has never been fully explored in the show. For instance, we could learn more about Darwin's life before he was adopted by the Watterson family. This could add depth and new perspectives to the character and the overall 'Amazing World of Gumball' universe.
One idea could be a crossover with 'Adventure Time'. Gumball and Finn could go on a wild adventure together, facing challenges in a mixed - up world of both shows. Maybe they have to find a magical item that got lost between their universes.
One plot idea could be that Gumball loses his braces and has to go on a wild adventure to find them before his next orthodontist appointment. Maybe they got accidentally mixed up with Darwin's fishbowl accessories and are now at the bottom of the ocean.