Obviously, Marinette herself is a must - include. She's the main character and the heart of the story. Adrien is also important as he is Marinette's love interest and also has his own secret identity as Chat Noir. Alya is a great character to add as Marinette's best friend. She can provide support, comic relief, and sometimes get involved in Marinette's adventures in an unexpected way. Another good character could be the school principal. They can create obstacles for Marinette, like strict rules or disapproval of her activities. And of course, Tikki, Marinette's kwami, who gives her the power to become Ladybug and offers advice.
Meowth would be a great addition. He could provide comic relief while also being part of Team Rocket's adventures related to the lemon theme. Also, Pikachu could be involved. Maybe Jessie and James try to use lemons to attract Pikachu in a new and strange way. And Butterfree, as it could be related to the pollination of lemon trees in the fanfiction.
Temari could be a great addition. As Gaara's sister, she could play a role in either supporting or being skeptical of their relationship. Naruto could also be included. His friendship with both Gaara and Sakura could add some interesting dynamics. He might be the one to encourage them or accidentally create some comical misunderstandings. Kankuro could be another character. He could provide some insights into Gaara's past and how his relationship with Sakura might change things in the Sand Village.
One common plotline could be Marinette facing a difficult school project while also dealing with her secret identity. For example, she might have to design a costume for a school play but is constantly distracted by Chat Noir's unexpected visits. Another plotline could involve a new student at school who becomes a rival for Marinette's affections towards Adrien. This new character might try to outdo Marinette in everything, from academics to fashion design. A third popular plotline might be Marinette having to deal with a strict teacher who doesn't understand her creative process and tries to make her conform to traditional ways of doing things, all while she's still trying to save Paris as Ladybug.
Alice would be a great character to include. Since she can see the future, she could add an element of mystery and foreshadowing to the side story. For example, she could give hints about the relationship between Carlisle and Bella that they themselves haven't realized yet. Jacob could also be included. His werewolf nature could contrast with Carlisle's vampire nature, creating some interesting interactions especially if they both have an interest in Bella's well - being.
Add in Rose Hattenbarger. Her sweet nature can balance out the more complex personalities of Lemon and Lavon. Tom Long is another good choice. His business - mindedness can create some interesting storylines when combined with Lemon and Lavon's ideas. And Shelby Sinclair. Her presence can stir up some jealousy or competition, especially if there are any romantic undertones between her and Lavon or Lemon. This can add more drama and conflict to the multi - character story.
Dallas could be a great addition. He has that tough exterior and his relationship with Johnny and Ponyboy is complex. His presence could add some drama and conflict. Another good character could be Sodapop. He's Ponyboy's brother and his kind and fun - loving nature could balance out the more intense moments between Johnny and Ponyboy.
Petunia could be a great addition. Her relationship with both Harry and Vernon adds a lot of complexity. She could be the mediator or the one causing more trouble between them, depending on the plot.
Raphael could be a character to include. He might initially be skeptical or even opposed to Leonardo's relationship with Karai due to her past actions. His presence could add some internal conflict within the group. Also, Shredder could be in the background as a looming threat, which could heighten the tension in their relationship as they try to keep it a secret from him.
Edward could also be included. His relationship with Rosalie as her adoptive brother and his complex feelings towards Jacob could create a lot of tension and drama. He could be a voice of reason or a source of conflict, depending on the direction of the fanfiction.
Chat Noir is an obvious choice. His relationship with Ladybug is so central to the original story, and with her pregnant, his reactions and support would be a great addition. Marinette's best friend Alya could also be included. She could be the one Ladybug confides in, and Alya could use her journalistic skills to help keep Ladybug's pregnancy a secret if needed. And Master Fu could be in the story. He could offer his wisdom and guidance, especially when it comes to any potential threats to Ladybug or the unborn child.