A really interesting plot would be if the characters from Alice in Wonderland were students at Hogwarts. Alice could be in Gryffindor, always getting into strange adventures around the school that remind her of Wonderland. The Mad Hatter could be a Potions master who makes the most bizarre potions. And the Red Queen could be a strict teacher who is always trying to catch students breaking the rules. There could also be a plot where Voldemort tries to take over Wonderland for some dark purpose, and Harry and his friends have to stop him there.
Well, think about this. What if the Time - Turner from Harry Potter was used to travel to Wonderland? Harry or Hermione could end up there and have to figure out how to get back. Or, imagine that the magic in Wonderland is different from the magic in the Harry Potter world, and a group of Hogwarts students go there to study it. There could be a conflict when some of the Wonderland creatures don't like the wizards interfering. Also, a plot where the Sorting Hat gets lost in Wonderland and the characters there have to figure out which Hogwarts house it belongs to could be really fun.
One idea could be that Alice returns to Wonderland as an adult and finds it has changed completely. The once friendly characters are now in a state of chaos due to a new dark force. Another could be a story where Wonderland is connected to our world in a more secretive way, and Alice has to keep the balance between the two. Or perhaps a fanfiction where Alice teams up with the Cheshire Cat to solve a mystery that involves all the Wonderland characters and their forgotten pasts.
One interesting plot could be a time - travel story in the Harry Potter wonderland. For example, a character goes back in time to the Marauders' era and gets involved in their adventures, while also trying to prevent a future disaster in the wizarding world. Another idea is a story where a new, powerful magic is discovered in the wonderland, and Harry and his friends have to figure out how to control it before it falls into the wrong hands. A third plot could be about an alternate reality where Voldemort won the war, and the remaining good characters have to find a way to reverse the situation in the harry potter wonderland.
One idea could be Harry finding a hidden portal in Hogwarts that leads him to Wonderland. There, he meets the Cheshire Cat who helps him understand some of the mysteries of the wizarding world in a different way. Maybe he has to solve Wonderland - like riddles to get back to Hogwarts.
Well, perhaps in the fanfiction, the Queen of Hearts is allergic to lemons. And Alice, unknowingly, brings lemons into the Queen's court. This causes chaos as the Queen starts sneezing and her usual angry outbursts are now mixed with her allergy-induced irritation. It could lead to a series of comical and adventurous events as Alice tries to fix the situation.
In some fanfiction, Harry could be the one who enters Wonderland. Maybe he's on a quest there, and he meets the Cheshire Cat. The Cheshire Cat could guide him, but in a very mysterious way, just like how Dumbledore often gives cryptic advice to Harry. Harry would have to adapt his magical skills learned at Hogwarts to the strange magic of Wonderland.
One idea could be that Alice returns to Wonderland as an adult and has to deal with new, more complex riddles and challenges that are related to the grown - up world she now knows. For example, the Queen of Hearts might be having a 'tax collection' problem in her kingdom and Alice has to use her real - world knowledge of economics to solve it.
A great fanfic idea could be a crossover where Voldemort tries to take over Wonderland. The characters from Wonderland, along with the help of the 'Harry Potter' gang, have to fight against him. The magical creatures in Wonderland, like the Jabberwocky, could team up with the magical creatures from the 'Harry Potter' universe, such as hippogriffs, to defeat Voldemort.
One idea could be that Alice somehow ends up in Neverland. Maybe she falls through a rabbit hole that magically transports her there. She could meet Peter Pan and the Lost Boys, and they all get confused by her strange Wonderland ways. For example, her size - changing could be a mystery to them.
One idea could be to explore what happens if Alice returns to Wonderland as an adult. Maybe she has forgotten all about it, and then something in the real world triggers her memories and she's pulled back. Another idea is to focus on the backstories of the characters she met in Wonderland. For example, the Mad Hatter's past could be a really interesting plot to develop.
One idea could be Harry finding himself in Wonderland during a strange magical accident at Hogwarts. He could encounter the Cheshire Cat as a magical creature that can disappear and reappear, leading him on a quest to find a way back home while also uncovering secrets about the Wonderland's connection to the wizarding world.