One possible aspect of a Naruto and Monster High fanfic could be the characters' interactions. For example, Naruto's determination and positive attitude might clash or blend with the unique personalities of the Monster High characters. Maybe Naruto could teach them about his ninja way, while the Monster High students introduce him to their spooky yet fun world.
One idea could be a crossover where the characters from Monster High end up in the Naruto universe. For example, Draculaura could use her vampire powers in a unique way during a ninja battle. Maybe she can turn into a bat to avoid attacks or use her charm ability on some of the ninja opponents.
He could also get angry. After all, being misjudged like that is unfair. His anger could lead him to either lash out verbally at Sakura or he could leave the village in a fit of rage, feeling that he is not accepted even by his friends. This could then lead to a series of events where Naruto has to find his own way and Sakura realizes her mistake later on.
Kakashi would be the most perceptive. He'd see how Naruto singing 'Monster' is not just a random act but a way for Naruto to connect with his own fears and insecurities. His friends from the Hidden Leaf Village would overall be proud of Naruto for trying something new and for using the song to share a part of himself that they may not have fully understood before.
Sasuke would likely be deeply affected. He might initially be angry that he couldn't protect Naruto. As Naruto becomes a monster, Sasuke would be conflicted between his desire for power and his loyalty to his friend. He might try to find a way to bring Naruto back to normal so he can have his rival back. Sakura would be heartbroken. She would probably cry a lot and then try to find a medical solution to reverse the transformation. Kakashi would see it as his failure to protect Naruto and would do everything he could to stop the monster Naruto from causing harm while also looking for a way to save him.
Kakashi would be very observant. He would look for how the fanfiction writers understand the world of Naruto, the values and the moral lessons. He might even use some of the creative ideas from the fanfiction in his own teachings if he thought they were valuable and in line with the spirit of the original story.
The plot could involve a quest. Maybe a powerful artifact from the Naruto world has ended up in Monster High, or vice versa. Naruto and his friends have to travel to Monster High to retrieve it. Along the way, they face challenges like dealing with the school's spooky environment and making friends with the Monster High students.
A popular pairing could be Naruto and Draculaura. Their personalities are quite different, with Naruto being the energetic ninja and Draculaura being the sweet vampire. The contrast between them could create some really interesting relationship dynamics in the fanfiction.
One interesting Naruto Monster High fanfiction could be where Naruto attends Monster High as an exchange student. He might show off his ninja skills during gym class or make friends with the unique monster students. Maybe he'd have a friendly rivalry with Draculaura in a race.
In this fanfiction, Naruto might go to Monster High to seek some kind of special power or knowledge. He could make friends with the monster students, like Frankie Stein. Together they could face challenges like a bad guy who wants to disrupt the harmony between ninjas and monsters. Naruto would use his Rasengan while Frankie uses her electricity powers to fight the enemy.