Yes, there are some out there. You can start by looking on popular fanfiction websites like Archive of Our Own. Just search for 'Harry Potter x Harley Quinn' and you'll find a variety of stories, from crossovers where Harley Quinn somehow ends up in the Harry Potter universe and causes chaos, to more complex stories where the two characters' personalities and backstories are intertwined in unique ways.
There might be. Check fanfiction.net too. Some writers might have been inspired to create a crossover between these two very different universes. However, the quality can vary a great deal. Some might focus more on the comical aspect of Harley Quinn in the magical world of Harry Potter, while others could attempt a more serious take on how their different powers and mentalities interact.
Chapter 610, "Building a House?!", is the clearest early answer because it turns Shang Shuyue's situation into a concrete plot event.
A practical answer is Chapter 15, because it turns the idea into a concrete scene. The chapter opens with Jiang Shixu woke up from those nightmares filled with blood and darkness,..., adds pressure through Jiang Shixu's mind was starting to cloud, but for some reason, when he..., and ends on Since.
The best chapter pointer here is Chapter 20, "Miss Su, your defense is somewhat clumsy". It opens with Several people turned their heads upon hearing the sound and saw three... and closes on So, he turned and questioned Jiang Li..
Chapter 806, "Flip the Table!", is the clearest early answer because it turns Jiang Zhao Yuan's situation into a concrete plot event. Early on, Jiang Li looked at the dining room that seemed to have been hit by a.... By the end, In an instant, the dining room fell silent..
Chapter 825, "This method is absolutely not feasible!", is the clearest early answer because it turns Qixing Tower's situation into a concrete plot event. The chapter turns that into something concrete by moving from Beside him, Yu Qing: "....." Why does it feel like neither of them...
Look to Chapter 15 for the clearest answer. It begins with Jiang Shixu woke up from those nightmares filled with blood and darkness,..., keeps building through The two sleeping pills he took in the evening had left him with a..., and lands on Since she didn't move, Jiang Shixu also stayed put, and.
Chapter 926, "Doomsday Beehive Exploded?!", is the clearest early answer because it turns Yu Fei's situation into a concrete plot event.
If you want the clearest chapter reference, go to Chapter 2. Early on, On the top floor of the Financial Building, a gathering of dark clouds...; later, the chapter leans on How dare Jiang Li hang up his phone?.
The best chapter pointer here is Chapter 21, "Uncle Policeman, They Are the Ones Causing Trouble!". It opens with Jiang Li's clear and logical explanation had everyone stunned in place. and closes on But the implications could be different..
A practical answer is Chapter 379, because it turns the idea into a concrete scene. The chapter opens with Aberdeen City, 1 year prior Inside a high-end hotel room penthouse,..., adds pressure through He rubbed his palm against her cheek and grinned., and ends on His wife gave him a bespoke Swiss.