Well, one idea could be that Percy has to face some sort of new mythical creature while in the 'Muck' setting. Maybe it's a creature that thrives in muddy and dirty places and has some special powers related to that. And the 'lemon' aspect could be added as some sort of a strange fruit or potion that has an unexpected effect on him or his quest.
Perhaps in this fanfiction, the 'Muck' represents a corrupted part of the Percy Jackson world. Percy has to 'handle' it by finding a way to cleanse it. And the lemon could be a symbol of purity that he needs to use in some ritual. For example, he might have to find a magical lemon tree in the muck that holds the key to restoring the balance.
The characters can be developed by giving them new relationships based on the setting. In the muck, they might meet new characters who are native to that area. Percy could learn from them how to survive in the muck. The lemon could play a role in these new relationships. For example, it could be a gift that Percy gives to a new friend in the muck, which helps to build trust. And as for his existing friends, they could have different reactions to the muck and the lemon, which shows more about their personalities.
A plot could be that Sally Jackson plants a lemon tree in her garden that turns out to be a gift from a minor goddess. The lemons from this tree have the power to give those who eat them the ability to see through illusions for a short time. Percy uses these lemons to his advantage when he is on a mission to retrieve a powerful artifact that is guarded by a monster that uses illusions to protect it.
Well, perhaps Aphrodite decides to give Percy a love lesson. Since he has had some rocky relationships. She could take him on a journey through different love stories in Greek mythology, showing him how to handle different situations. And as for the lemon part, it could be a situation where Aphrodite uses her charm to make Percy feel a bit flustered and his face turns red like a lemon. It would be a cute and funny scenario.
Well, perhaps a plot where Percy discovers that his father has a secret lemon - related past. Maybe Poseidon once made a deal with a lemon - loving deity and now there are consequences. For example, every time Poseidon gets angry, lemons start falling from the sky around Percy. This could lead to all sorts of humorous and adventurous situations as Percy tries to figure out how to break the curse.
One idea could be the hellhound having a secret bond with Percy. Maybe it starts out as a dangerous encounter but as Percy tries to understand the hellhound's motives, they form an unexpected alliance. This could lead to them facing off against common enemies in the Percy Jackson universe.
One idea could be Calypso using her powers to help Percy in a new and unexpected way during a quest. Maybe she creates a special lemon - scented shield that can protect against a certain type of monster.
One idea could be a crossover adventure where Percy Jackson teams up with the Wolf Lemon characters to face a new and powerful enemy. Maybe a threat that combines the magic from the Percy Jackson world and the unique abilities of the Wolf Lemon world.
One idea could be Percy joining the hunt and having a series of misadventures with the hunters. Maybe there are some magical challenges that only he can solve due to his unique skills. Another could be a budding romance between Percy and one of the hunters, which causes some tension within the group as they have to deal with the rules of the hunt. And perhaps there could be a new prophecy related to the hunt that Percy has to figure out, leading to an epic journey.
One idea could be that Percy, after his encounter with the Minotaur, discovers a lemon tree in the Camp Half - Blood that has some magical properties related to the Minotaur. Maybe the lemons can be used to create a potion that can temporarily weaken the Minotaur's strength. Another plot could involve a lemon - themed quest where Percy has to retrieve a golden lemon that the Minotaur is guarding. It could be a symbol of power that the gods want to keep away from the monsters.
A great plot could be about Zoe Nightshade teaching Percy some ancient hunting techniques that were long forgotten. This would not only strengthen their bond but also give Percy an edge in future battles. It's a plot that focuses on their friendship and mutual growth without any inappropriate elements.