You can try searching on fanfiction websites like Archive of Our Own or FanFiction.net. Just type in 'Lucy Frosch Fairy Tail' in their search bars, and you might find relevant fanfictions.
In some fanfictions, Lucy might be portrayed as a friend to Frosch. She could be someone who looks out for the little Exceed, given her kind - hearted nature in the Fairy Tail series.
One popular theme is the bond between Rogue and Frosch. Writers often explore how deep their connection is and how they support each other through different challenges. Another theme is adventure. Given the nature of Fairy Tail, fanfictions may feature Rogue and Frosch going on exciting quests.
Another place to check could be Reddit. There are specific subreddits dedicated to Fairy Tail fanfiction. You might find some great Rogue and Frosch fanfictions shared by fellow fans there. Sometimes, fans also discuss their favorite stories and authors, which can be a great lead for you to discover more.
I really like 'Fairy Tail: Sisters in Arms'. This fanfic focuses on the strong friendship between two female characters that could be seen as more. It has exciting adventure scenes where they rely on each other, and the author does a great job of showing their emotional connection through their actions and dialogue.
Gray Fullbuster can often be portrayed as a bad boy in fanfiction. His cool and sometimes aloof attitude, along with his stripping habit which can be seen as a bit of a rebel trait, makes him a popular choice. Another one could be Gajeel Redfox. He was originally an enemy but joined Fairy Tail. His rough past and tough exterior give him that bad boy vibe.
Perhaps Natsu is seen as a bad boy because he's from a different background than most of the students at Fairy Tail School. He might come from a poorer part of town and has a rougher attitude. He could be constantly getting into fights with the rich kids who look down on him, and through these conflicts, he learns about friendship and acceptance.
If Natsu turns into a girl in fanfiction, his appearance would be quite a change. He might have long pink hair, and his eyes could be even more expressive. His usual dragon - slayer outfit would have to be adjusted to fit his new female form, perhaps becoming more form - fitting or having some feminine touches. In terms of his magic, it would remain the same, but the way he uses it could be different. He might be more strategic, using his new - found grace to his advantage in battles.
One possibility is that it would bring a whole new dynamic to his relationships. His friends, like Gray, might be really confused at first. Natsu, as a girl, could potentially show a more delicate side while still having that fiery spirit. For example, in battles, she might use her strength in a more unexpected way, taking advantage of opponents underestimating her because she's a girl.
One interesting story could be about a bad boy character from Fairy Tail who has a hidden soft side. For example, a character who seems tough on the outside but is actually very kind to animals in secret. Another might be a story where the bad boy is on a journey of redemption, trying to make up for past mistakes within the Fairy Tail guild.