A magical portal could be created. In the Harry Potter universe, there are already powerful spells that can create portals. A wizard could accidentally or deliberately create a portal that links to the space captain's world. Or, the space captain's advanced technology could detect and open a rift in space - time that leads to the wizarding world.
Perhaps there is a magical object in the Harry Potter universe, like an ancient amulet. When combined with a specific energy source from the space captain's ship, it creates a bridge between the two worlds. Another way could be a powerful magical being from the Harry Potter world, like a phoenix. It has the ability to traverse different realms and could carry the space captain or a character from Harry Potter to the other world.
There could be a prophecy in the Harry Potter world that predicts the coming of the space captain. This prophecy could be the key to unlocking a natural gateway between the two worlds. On the space captain's side, his ship could be equipped with a device that was designed to seek out other dimensions. When it detects the magical energy of the Harry Potter world, it creates a connection, allowing the crossing between the two.
One idea could be that the Space Captain crash - lands on the magical world of Harry Potter. He has to learn about magic to repair his ship while Harry and his friends are intrigued by the advanced technology the captain brings. Maybe they team up to fight a new threat that is endangering both the wizarding world and the space captain's galaxy.
One interesting crossover could be Matilda using her telekinetic powers in the wizarding world of Harry Potter. For example, she might use it to outwit some of the dark wizards or help Harry in a difficult situation. Maybe she could even use it during a Quidditch match to change the course of the game in Gryffindor's favor.
Well, some fanfics blend the two worlds by making 5sos be related to some wizarding families. So, they already have a connection to the wizarding world without really knowing it. Then, as they discover their heritage, they get involved in the Harry Potter storylines. It could be that one of the 5sos members has a long - lost wizard relative and that's how they are drawn into the magical universe. This way, the two worlds are intertwined in a more family - based way.
One way is through a portal. For example, a magical portal could open up between Hogwarts and Neverland. This allows characters from both worlds to interact. Harry Potter could enter Neverland and be shocked by the lack of traditional magic but also find unique magical elements there related to the island's magic. Captain Hook could enter Hogwarts and be amazed and also threatened by the powerful magic there.
In a fanfic, the magical and Pokemon worlds could merge due to a spell gone wrong. Alain could befriend some of the Hogwarts students and introduce them to Pokemon. The Hogwarts grounds could become a new place for Pokemon training, with spells and Pokemon abilities interacting in interesting ways. For instance, a Pokemon's electric attack might interact with a Lumos spell in an unexpected way.
Definitely Doctor Octopus. Imagine him getting his hands on some magic wands and using his mechanical arms to perform complex spells. He could be a really formidable villain in the wizarding world, and it would be exciting to see how Harry Potter and Spiderman would team up to stop him.
It could combine them by having the rocket launcher be a magical object. For example, it could be created by a wizard who was fascinated by Muggle technology. The launcher's power source could be magic, like it runs on unicorn tears or something. And the way it's used in the wizarding world would be different from how Muggles use it. Instead of normal explosives, it could fire spells or magical creatures.
It could be that the Ministry of Magic decides to collaborate with Tony Stark. They see the potential of the Iron Man suit in fighting dark magic. So, they bring Stark to Hogwarts to work with the students. Harry and his friends would then get to learn about engineering and technology from Stark while also teaching him about magic. This would lead to a really interesting combination of the two worlds, with new spells and tech - based magic being created.
The plot could involve Naruto characters being transported to the X - Men world or vice versa. They might team up to face a common threat that is affecting both worlds, like a powerful villain who is stealing chakra and mutant powers. Maybe Naruto and Wolverine could bond over their shared experiences of having a power within them that they have to constantly control.
One way the worlds could collide is through a magical accident. Maybe a spell in the Harry Potter universe goes wrong and opens a portal to the Tokyo Ghoul world. The wizards could be shocked to see the ghouls with their kagunes. And the ghouls would be equally surprised by the magic of the wizards.