In this fanfiction, Ash's personality might change in terms of his patience. Since Growlithe is not just another Pokémon he's training but has a special connection with, he'll need to be more patient. He might learn to read Growlithe's body language and moods better. Growlithe's personality could develop by becoming more confident. With Ash's support, it could face bigger challenges and become more of a leader among Pokémon, while still relying on Ash for emotional support.
Ash could be shown as more empathetic towards Growlithe. His usual determination to be a great trainer could be combined with a newfound protectiveness over Growlithe. For Growlithe, it could be developed as being more curious about Ash's world and trying to adapt to human ways while still maintaining its Pokémon instincts.
Eevee's personality could be developed by highlighting its adaptability. It can be shown as being able to quickly adjust to new situations, whether it's a new environment or a new group of Pokémon. Growlithe, on the other hand, can have its stubborn side shown. For example, when it decides to protect Eevee, it won't be swayed by other Pokémon's opinions or attempts to stop it. This can lead to some interesting conflicts and also deepen the relationship between the two as they learn to work around each other's traits.
For Bumblebee, his usually brave and somewhat impulsive nature can be developed further. In the fanfiction, he could face situations where his impulsiveness gets him into trouble, and he has to learn to be more cautious. Smokescreen, on the other hand, who is often eager and a bit naive, could be put in situations that force him to become more worldly - wise. For example, he might encounter deception and learn to be more discerning.
For Optimus, his sense of duty and leadership can be further explored. In a fanfiction, we can show how he balances his leadership role with his personal relationships, like with Bumblebee. For example, he might struggle between making the tough decisions for the group and protecting Bumblebee from harm.
For Pikachu, you could develop his curious side more. Maybe he's always eager to explore new areas in the fanfiction, which sometimes gets him into trouble. Sylveon could be shown as the more cautious one, using its ribbons to hold Pikachu back when he's about to rush into danger.
Lucy's personality can be developed by putting her in different scenarios at Happy Lemon. Say she's a bit of a perfectionist. At Happy Lemon, she might notice that the presentation of the drinks isn't always perfect. Instead of just complaining, she could start helping the staff to improve it, which would make her more understanding and less critical. As for the Happy Lemon characters, like the employees, if they start off as a bit lazy, they could be inspired by Lucy's enthusiasm to become more hard - working and take pride in their work. You can also have Lucy introduce new ideas to the Happy Lemon crew, which would make them more open - minded over time.
For Ash, his already existing determination can be further emphasized when it comes to protecting Plusle and Minun. He could show more patience in teaching them new things. May could become more confident in her decision - making. Maybe she takes the lead in some situations involving Plusle and Minun. For Plusle and Minun, their playfulness can be a starting point. As the story progresses, Plusle could become more cautious while Minun could grow to be bolder.
For Naruto, his usual determination and cheerfulness can be maintained but with a new layer of vulnerability when it comes to his relationship with Madara. He might be more hesitant and shy in expressing his feelings at first. Madara, on the other hand, could have his stoic and powerful facade start to crack as he falls for Naruto. His cold exterior could give way to a more protective and affectionate side.
For James Bond, his suave and confident nature can be emphasized through his interactions with Jinx. He could show his intelligence and resourcefulness when they are in tight situations. Jinx, being a strong - willed character, can be developed by showing her determination. For example, when she has a different approach to a problem than Bond, she stands her ground. This way, their personalities clash and complement each other at the same time.
Well, I don't really recommend writing lemon fanfictions as they often cross the line of propriety. But if you must, focus on the emotional connection between Ash and Growlithe first. Build up their relationship in a deep and meaningful way before any sort of 'lemon' elements are introduced. And make sure to use euphemisms and not be overly explicit.
For the OC, you can start by giving them a distinct backstory. If they had a tough childhood, it might make them more resilient and street - smart. This could contrast with Android 18's initially cold and detached personality. The OC could gradually break through Android 18's walls with their kindness and determination. For Android 18, her experiences with the OC could make her more open and empathetic. Maybe she starts to care more about the well - being of others, especially the OC.