I'm not sure if it's popular. There are so many fanfics out there that it's hard to gauge the popularity of one specific one without looking at relevant fanfic platforms and their statistics.
The title 'spooky's house of jumpscares lemon fanfic' is rather mysterious. 'Spooky's house of jumpscares' sounds like a story set in a haunted or creepy location where there are lots of sudden frights. As for the 'lemon' part in fanfic, it can mean different things. It might be that there are some steamy or suggestive scenes in the story, but it could also just be a term used to make the title more eye - catching or unique. Without actually reading the fanfic, it's difficult to be more precise about its content.
It could be a story where some of the GTA 5's nightclubs or amusement parks have animatronics that come to life at night. These animatronics could start stalking the players, much like in FNAF. They might be found in the dark corners of the city, with glowing eyes, and make strange noises as they approach the player.
Well, in a Harry Potter and FNAF crossover fanfiction, the magic of Harry Potter could interact with the horror of FNAF in unique ways. The Death Eaters could use the animatronics as some sort of dark weapon. And Harry and his friends would have to use their spells and magical skills to stop them. Also, the Hogwarts houses could have different reactions to the animatronics. Gryffindors might be brave enough to confront them directly, while Hufflepuffs might try to befriend them in a way.
There could be a villainous character in the fanfic as well. This could be a dark entity that controls the house of jumpscares and is trying to keep Naruto trapped inside. So Naruto, his potential friends who come to his aid, and this villainous entity would be the main characters in the story.
One possible plotline could be Naruto facing his fears within the spooky house. Maybe he discovers that the jumpscares are actually illusions created by a rogue ninja using genjutsu. Another could be Naruto teaming up with some of the spooky entities in the house to defeat a greater evil that lurks outside.
Definitely not a true story. FNAF is a work of fiction that takes place in a fictional world with its own set of rules and scenarios. It's all about creating a thrilling and immersive gaming and storytelling experience, not reflecting reality.