A plotline might involve Harry being reincarnated as Smaug in a parallel universe. As Smaug, he remembers his past life as Harry and tries to use his knowledge of magic to rule over the lands in a more benevolent way than the original Smaug. Or perhaps there is a prophecy that states only a wizard - turned - dragon can save both the wizarding world and Middle - earth from a great evil, and Harry is the chosen one to become Smaug.
One possible plotline could be that Harry Potter sacrifices himself to defeat an even more powerful dark wizard than Voldemort. Maybe this new enemy has a power that can only be countered by Harry's self - sacrifice, which would lead to a very bittersweet ending for the wizarding world.
One possible plotline could be Naruto trying to find a way to visit the Harry Potter world. He might search for some kind of magical portal or a powerful spell that can transport him there. Another plotline could be Naruto using the ideas from Harry Potter books to improve his ninja techniques. For example, he could learn about the concept of wandless magic and try to apply it to his chakra control.
One possible plotline could be that Harry is cursed and slowly turns into a dragon. As he changes, he has to deal with the physical and mental challenges of this transformation. His friends would try to find a way to reverse the curse while Harry struggles to control his new instincts.
A plotline could involve a Zorua being brought to Hogwarts by a new transfer student from a far - off land. This Zorua has special powers that are not fully understood in the wizarding world of Harry Potter. The student is initially shunned because of the strange creature, but Harry and his friends see the potential good in it. As they get to know the Zorua, they discover that it can help them in their fight against Voldemort. Maybe it can create illusions to mislead Death Eaters or use its shape - shifting abilities to infiltrate their ranks.
In a 'poison Harry Potter fanfic', a plotline might involve a poisoning attempt on a major character like Dumbledore. This could send the whole wizarding world into chaos as they try to figure out who the culprit is. Harry, Hermione, and Ron would then be on a quest to find out the truth. They might suspect Snape at first, but as they dig deeper, they discover a much more complex conspiracy involving other dark wizards. Another possible plotline could be that a magical poison is used to control the minds of some wizards, and Harry has to break the spell and find the antidote to save his friends and the wizarding world from being taken over by the poison - controlled minions.
One possible plotline could be that a new strain of magical typhus breaks out in Hogwarts. The students and teachers have to figure out how to contain it while also dealing with the regular Hogwarts drama. Maybe Hermione tries to research a cure using both magic and Muggle medicine knowledge.
One possible plotline could be Harry finding a way to secretly practice magic while imprisoned. For example, he might discover a hidden corner in the attic where he can perform small spells without the Dursleys noticing.
Perhaps Harry Potter gets lost in a mysterious Chinese magical forest. In this forest, he encounters ancient Chinese magic that is both fascinating and dangerous. He has to use his existing skills from Hogwarts along with what he learns in this new environment to find his way out and also figure out why he was abandoned in China in the first place.
One plotline could be Harry starting his bakery in Diagon Alley. He might face some initial resistance from the more traditional wizarding families because of his sexual orientation, but gradually wins them over with his delicious magical baked goods. Another could be that he uses his baking skills to raise funds for a magical LGBT+ organization in the wizarding world.
One possible plotline could be that as a female Harry Potter, she discovers the world of One Piece and becomes a huge fan of Shanks. Maybe she tries to incorporate some of the values she admires in Shanks, like his loyalty and courage, into her fight against Voldemort. For example, she might be inspired by Shanks' selfless act of sacrificing his arm to save Luffy and be more willing to put herself in danger to protect her friends at Hogwarts.