One idea could be that Spider - Man finds himself magically transported to the wizarding world of Harry Potter. He could use his web - slinging skills in Hogwarts, perhaps to help catch the Golden Snitch during a Quidditch match in a very unorthodox way. The Hogwarts students would be both amazed and a bit confused by this strange new hero in their midst.
Another concept could be that Harry Potter and his friends visit New York City where Spider - Man operates. Harry, Hermione, and Ron could team up with Spider - Man to fight against a dark wizard who has teamed up with some of Spider - Man's villains. This would be an interesting crossover as they combine magic and superhero powers to save the day.
Perhaps there could be a story where a spell gone wrong in the wizarding world creates a portal that sucks in some of Spider - Man's technology. Spider - Man follows it to the wizarding world and has to learn how to use magic in order to get his technology back. Along the way, he befriends some of the Hogwarts students and they help him on his quest.
Maybe the Venom symbiote could find its way into the Harry Potter universe and attach itself to a wizard. This wizard would then have to struggle with the dark and aggressive nature of the symbiote while also dealing with the magical world's rules and expectations. Harry Potter and his friends would have to figure out how to separate the wizard from the symbiote without using traditional Muggle technology.
Perhaps in a fanfiction, Venom is actually a creation of one of the villains in Homecoming who wants to use it to defeat Spider - Man. But the symbiote has a mind of its own and instead starts to have an odd connection with Spider - Man, leading to a complex relationship where they have to figure out if they can trust each other.
Maybe Harry Potter and his friends visit Stark Tower in the Marvel universe. They are amazed by all the advanced technology there. Iron Man could be intrigued by magic and try to figure out how it works, leading to some really interesting interactions between science and magic.
One idea could be a crossover where the Pillar Men are somehow transported to the wizarding world of Harry Potter. They might initially be seen as a threat, but then find common ground with some of the darker wizards who are interested in their unique powers.
One idea could be that Spider - Man has to save Zootopia from a new villain. Maybe a super - intelligent criminal who has found a way to control the minds of some of the animals. Spider - Man would have to use his web - slinging skills and his intelligence to stop this villain without causing too much chaos in the city of anthropomorphic animals.
Perhaps in the fanfiction, there is a plot where a powerful enemy is targeting young superheroes. Peter and Wanda find out about this and decide to form an alliance. They start training together to improve their skills. Peter learns how to be more strategic from Wanda, and Wanda learns about Peter's quick - thinking and adaptability. Their combined efforts lead to some epic battles against the enemy.
In a fanfiction, Spider - Man could get lost in an alternate dimension during a mission. The Avengers then have to find a way to bring him back. While in the alternate dimension, Spider - Man meets different versions of the Avengers and has to fight his way through various challenges to return home.
One idea could be a crossover where Spider - Man and One - Punch Man team up to fight a common enemy. Maybe a powerful villain from the Spider - Man universe has somehow made its way into the One - Punch Man world and is causing chaos. They could learn from each other's fighting styles. Spider - Man with his acrobatic moves and web - slinging, and One - Punch Man with his overwhelming strength.
One idea could be that Spider - Man gets accidentally transported to the Guardians' part of the galaxy. He teams up with them to fight a new threat that is endangering both Earth and the various planets in the Guardians' territory. His unique abilities, like web - slinging, would be an interesting addition to the Guardians' combat style.
One idea could be that Danny Phantom gets transported to the Spider - Man universe. He could use his ghost powers to help Spider - Man fight villains that are a bit more supernatural in nature, like Mysterio when he's using his illusions. Danny could phase through objects to avoid attacks and then surprise the bad guys.