One idea could be a time - travel plot where the protagonist goes back in time to meet the 'guy like you' at a different point in his life. Maybe they could change the course of events that led to the current situation in the original story.
A plot where the 'guy like you' character loses his memory and the other main character has to help him regain it while also falling in love all over again. It could add a new layer of depth and mystery to their relationship.
One idea could be a crossover with the Naruto and One Piece universes. Might Guy could end up on the Grand Line and his unique fighting style would shock the pirates. He might challenge some of the strong fighters there like Zoro to a friendly duel, showing off his Taijutsu skills.
An interesting plot could be an OC who is a noblewoman forced into an arranged marriage with Guy of Gisborne. At first, they clash due to their different personalities and loyalties. However, as they face common enemies and challenges together, they begin to develop feelings for each other. Or an OC who is a thief that Guy catches, but instead of punishing the thief right away, he uses the OC to gather information about other criminals in the area.
Another plot could be that the OC is a time - traveler who accidentally lands in Quahog. The female characters find his stories of different times and places fascinating. They start to form a harem - like group around him as they want to hear more about his adventures. Peter might initially be jealous but then end up getting involved in the OC's misadventures too.
A more complex plot could be that the entire Family Guy cast gets transported to Hogwarts during a school year. Quagmire could be the new Defense Against the Dark Arts teacher, bringing his own unique brand of 'defense' which mostly involves flirting with the female students. Lois could get into trouble for trying to organize a Muggle - style PTA at Hogwarts, and Peter could end up on the Quidditch team as an accidental addition.
A possible plot for a Family Guy Bonnie Lemon fanfiction could be that Bonnie starts to feel unappreciated at home. She decides to take a break and goes on a solo trip to a lemon orchard she read about. There, she meets interesting characters who teach her about the value of self - love and relaxation. When she returns home, she has a new outlook on life and starts to make changes. For example, she redecorates her living space with lemon - inspired decor to remind her of her journey. She also becomes more assertive in the family, demanding more respect from her husband and others around her.
One plot idea could be that the OC guy is a new hero in the game world where Neptune exists. He starts off as a bit of an outcast but Neptune sees his potential. They go on adventures together to save the game world from a new virus threat. As they journey, they start to develop feelings for each other through shared hardships and victories.
Well, you could write a fanfiction where Meg finally finds true friends who appreciate her for who she is. Maybe a story where Lois discovers a hidden talent and pursues it, causing chaos in the family. Also, a tale about Quagmire having a serious relationship and how it affects his womanizing ways could be interesting.
One idea could be an average guy suddenly gaining a power similar to Saitama's but in a very limited way. He tries to use it to help in small ways around his neighborhood, like stopping petty thieves or helping old ladies cross the street. But he constantly struggles with not being able to fully control it, leading to some comical situations.
One plot idea could be that Sakura dresses up as a guy to enter a male - only competition, like a martial arts tournament. There, she has to hide her true identity while facing tough opponents and making new friends. Another could be she disguises as a guy to spy on an all - male group for some important information. And also, perhaps she dresses as a guy to attend an exclusive boys' school and experiences a whole new world of friendships and rivalries.
One idea could be creating an OC who is a new neighbor in Quahog. This OC could have a really strange hobby like collecting antique doorknobs. They could get involved in the Griffin family's chaos, for example, when Peter tries to borrow a doorknob for some wacky project. Another idea is an OC who is a foreign exchange student at Chris's school. This OC could introduce new cultural elements to the show's typical American setting, leading to funny misunderstandings.