One way to blend the two universes is through the use of magical artifacts and Cybertronian technology. Maybe the Philosopher's Stone could be used to power up Optimus Prime in some way, or a Cybertronian device could be used to enhance a wizard's magic. This creates a connection between the two universes where they rely on each other's unique elements.
Well, it blends them by combining the magic of the Harry Potter universe with the superpowers of Superboy. For instance, in such fanfiction, Superboy might have to deal with the laws of magic which are completely different from what he's used to in his own world. His super strength might be affected by anti - magic spells, or his flight ability could be disrupted by magical fields.
Well, it often has Harry using Hitman - like skills. For example, stealth and precise attacks. In some fanfics, he might use magic to enhance these skills. Like using a silencing charm while sneaking up on an enemy, just like a hitman would use his training to be quiet.
Well, it often blends the two by having characters from one universe enter the other. Like a Supernatural character might end up in the wizarding world through some sort of magical portal or spell gone wrong. Then they have to adapt to the new rules and powers there.
In fanfiction, the two universes blend in multiple ways. The characters from Harry Potter can be put into Creepypasta - like situations. For instance, Harry might find himself in a situation where he has to face a entity that is not from the wizarding world but from a Creepypasta realm and has to use his magic in a new and untested way to survive. Also, the magic in Harry Potter can be warped to fit the spooky nature of Creepypasta. Spells could have unexpected and disturbing side - effects that are more in line with Creepypasta. The creatures in Harry Potter can also be made more menacing by borrowing elements from Creepypasta. For example, a Hippogriff could be made to look more like a nightmarish beast with Creepypasta - inspired features.
One way is to establish a shared threat. Let's say there's a being that can travel between the two universes and is causing chaos in both. This forces the characters from Harry Potter and The Doctor to work together. In terms of world - building, describe how the different magics and technologies interact. For instance, the Time - Lords' time - travel abilities could be compared and contrasted with the time - turners in Harry Potter. The characters from both sides need to have believable reactions to the new elements of the other universe. Harry might be awestruck by the TARDIS, while the Doctor could be intrigued by the magic spells at Hogwarts.
In these fanfictions, they blend by sharing certain characteristics. For example, the loyalty and camaraderie among the characters in both universes are emphasized. In Harry Potter, it's the loyalty among the students of Hogwarts and the Order of Phoenix. In Kancolle, it's the bond between the shipgirls. This common trait can be a basis for the two universes to interact, like the shipgirls and the wizards/witches working together based on mutual trust.
The blend occurs through character adaptation. For instance, the characters from Harry Potter might adopt some of the attitudes and behaviors of gangsta characters. Hermione could be like the brains behind a gang's operations, using her vast knowledge in a more street - wise way. And the story might be set in a more urban, gritty environment which is typical of the gangsta genre while still having the magic of Harry Potter.
It could blend the two universes by having Godzilla - like creatures be the result of dark magic experiments gone wrong in the Potter universe. Or perhaps the magic in the Potter world could be used to control Godzilla's power. For example, a powerful wizard might use a spell to direct Godzilla's atomic breath to defeat Voldemort.
The blend could happen through the use of prophecies. Since Apollo is associated with prophecy in Greek mythology, the daughter could have prophecies that are different from the ones in the Harry Potter series but still relevant to the overall battle against evil. This would introduce a new layer of mystery and foreshadowing. Also, the daughter's connection to the sun, as Apollo is the sun god, could be used to counter the darkness associated with Voldemort. Maybe she can create light shields or use sunlight - based spells.
It could blend the two universes by having a shared threat. Let's say an evil force is using both dark magic and the power of the Star Destroyer to conquer both the wizarding world and the galaxy. Harry Potter and his friends would then team up with some of the more heroic characters from the Star Wars universe, like Luke Skywalker. They would combine their skills, with the wizards using magic to counter the dark magic and the Star Wars characters using their blasters and ships to fight the Star Destroyer - related threats. This would create a really interesting dynamic where two very different worlds have to work together.