In a fanfiction, there are no real limits. Percy could potentially lift Mjolnir if the writer decides to give him the qualities that would make him worthy in Norse terms. Maybe his loyalty to his friends, his courage in the face of danger, and his selfless acts could be seen as worthy traits. However, some fanfictions might also play with the idea that he can't lift it, but still has some sort of connection to it that leads to other interesting plot developments.
Well, in fanfiction, anything can happen. Percy Jackson might be able to lift Mjolnir. His character has shown great strength, both physical and moral. If the fanfiction writer wants to create a crossover where the rules of worthiness are a bit more flexible, Percy could easily lift the hammer. For example, if his actions in saving the world in the Greek mythology context are seen as equivalent to the deeds of worthy Norse heroes, then he could pick up Mjolnir and use its power for good, or it could lead to a whole new set of challenges as he tries to control this new power.
If you want the clearest chapter reference, go to Chapter 126. Early on, Wen Jiaojiao initially wanted to cause trouble.; later, the chapter leans on But when her gaze swept around and landed on Jiang Li, who was standing at....
Look to Chapter 132 for the clearest answer. It begins with The new girl in the live-streaming room went crazy., keeps building through Who is this handsome guy???" "Ahhh, so handsome, I'm gone, where is the..., and lands on He stir-fried the other dishes Jiang Li had prepared, and somehow.
If you want the clearest chapter reference, go to Chapter 106. Early on, Thinking of this, He Yun nodded with a hint of anticipation.; later, the chapter leans on Alright, then tell me my fortune, what do I need to do?.
If you want the clearest chapter reference, go to Chapter 91. Early on, When Jiang Li saw that he had been assigned a harrow, Qi Tianyu felt his...; later, the chapter leans on My tool couldn't possibly be a shovel, could it?" Director Sun chuckled....
Chapter 81 is the strongest chapter-level answer because it starts from Qi Tianyu, who chose curry beef rice, received a piece of curry and a... and follows through on The summer on the Southwest Plateau is no joke; the sun at three o'clock....
If you want the clearest chapter reference, go to Chapter 100. Early on, The barrage was about to die of laughter.; later, the chapter leans on [Hahahaha, help, why is the young master always being chased!] [Next door,....
Look to Chapter 130 for the clearest answer. It begins with This task, the first one, should have been his in the bag., keeps building through However, just as he was about to get out of the water and take a short..., and lands on Normally, the best planting distance for sweet potato seedlings is.
If you want the clearest chapter reference, go to Chapter 111. Early on, The main room's door was pushed open just a crack, and the head of the...; later, the chapter leans on Miss Jiang, you're still up, that's great..
A practical answer is Chapter 121, because it turns the idea into a concrete scene. The chapter opens with Seeing that Wen Jiaojiao's condition had improved significantly, Director..., adds pressure through How the hell was it a huge muddy field?!, and ends on You're supposed to be a man who.
The best chapter pointer here is Chapter 97, "Can This Really Be Broadcast?". It opens with Suddenly, Jiang Li's livestream room was packed with people, and the... and closes on And you believe what she says?.