Well, it's very likely that there is a 'Percy Jackson is the Joker' fanfiction out there given the popularity of both Percy Jackson and the Joker. But finding it might take a bit of effort. Firstly, as mentioned before, AO3 and FanFiction.net are good places to start. Additionally, Tumblr has a large fanfiction community. You can search for relevant tags. Sometimes, the tags might not be as straightforward, so you might have to dig a bit deeper. For example, you could look for tags related to 'Percy Jackson crossovers' and then see if there are any that involve the Joker character.
If you want the clearest chapter reference, go to Chapter 83. Early on, When they received the task, the three of them were already sharpening...; later, the chapter leans on He Yun had originally wanted to try making braised fish under Jiang Li's....
If you want the clearest chapter reference, go to Chapter 117. Early on, Fragrant and cloyingly sweet potatoes and corn were out of the pot, and Qi...; later, the chapter leans on The searing heat made him grimace in pain, but he didn't let go, and he....
Look to Chapter 38 for the clearest answer. It begins with Jiang Li had also observed the girl who had just entered., keeps building through Before arriving, she had briefly reviewed the profiles of the other three..., and lands on He Yun coldly turned his head and continued to maintain his aloof.
A practical answer is Chapter 97, because it turns the idea into a concrete scene. The chapter opens with Suddenly, Jiang Li's livestream room was packed with people, and the..., adds pressure through Master, you're the only one who can help me now., and ends on And you believe what she says?.
The best chapter pointer here is Chapter 59, "Kicked Out". It opens with After walking for about two or three hundred meters, the old man stopped... and closes on My phone, my cigarettes, my champagne, oh how I miss you......" He swore,....
The best chapter pointer here is Chapter 69, "Received Two Advertisements on the First Day". It opens with Since the phones issued by the program team couldn't log into Weibo, Wen... and closes on Wen Jiaojiao immediately hugged her arms proudly, specifically waiting to....
Chapter 57 is the strongest chapter-level answer because it starts from Lu Xingchao's numerous fans were stunned. and follows through on I'm saying, big bro, can you at least reply to me?.
Chapter 59 is the strongest chapter-level answer because it starts from After walking for about two or three hundred meters, the old man stopped... and follows through on My phone, my cigarettes, my champagne, oh how I miss you......" He swore,....
Chapter 99 is the strongest chapter-level answer because it starts from Seeing the man approach, one of the individuals with a long scar across... and follows through on Just as she was considering whether to practice a set of boxing, her phone....
A practical answer is Chapter 100, because it turns the idea into a concrete scene. The chapter opens with The barrage was about to die of laughter., adds pressure through Who would dare write a script like this!], and ends on Her eyes flickered slightly as she grabbed the hand..