Well, Percy's ability to control water and Frozen characters' ice powers could create some cool interactions. For example, Percy could make a stream of water and Elsa could freeze it to create an ice bridge. It would be a great way for them to traverse difficult terrains.
The vampires' super strength and speed in Twilight could be a match for the physical abilities of some of the stronger demigods in Percy Jackson. For example, Emmett's brute strength might be on par with that of a son of Ares. However, the demigods have their own unique powers. Percy's control over water could be a huge advantage. He could create water barriers to keep the vampires at bay, as vampires are not that great with water.
Percy would probably be very cautious around Morathi at first. Given his experiences with tricky and powerful beings, he'd be on guard. Morathi, being the conniving character she is, might try to charm Percy or manipulate him. For example, she could use her allure to make Percy lower his defenses, but Percy's loyalty to his friends and his own sense of right and wrong would likely make him resist.
Annabeth, if she were with Percy, would be more interested in the architecture and strategic planning of Troy. She could offer her knowledge to the Trojans or the Greeks, but they might not trust her either. And Percy would have to protect her from those who might see her as a threat or a sorceress.
Percy would probably be initially cautious when interacting with Egyptian gods. For example, when meeting Ra, the sun god, Percy might be in awe but also a bit hesitant as their powers are so different. He would need to show respect as he does with the Greek gods. The Egyptian gods, in turn, might be curious about Percy's abilities, especially his control over water which is not as prominent in Egyptian mythology.
If we think about it, Percy could use his ability to communicate with sea creatures to help the pirates. For instance, he could ask the dolphins to lead the ship to a safe place or warn them about incoming danger. The pirates would be amazed by this. Meanwhile, the demigods would be shocked by the pirates' lack of knowledge about the Greek gods but also impressed by their sailing skills and their ability to survive in a cut - throat world. The interactions would be full of misunderstandings at first but could grow into mutual respect as they face challenges together.
The demigods from Percy Jackson's world would interact with the Diablo characters in different ways depending on their personalities. Annabeth, being the strategic thinker, would try to analyze the Diablo characters' weaknesses and form plans. She might try to communicate with any intelligent Diablo creatures to find out more about their world. Grover, with his connection to nature, might be really disturbed by the corrupted and dark nature of the Diablo world. He could try to find any remnants of good or nature in that world to help in the fight against the dark forces. And when it comes to the Diablo characters, some of the more cunning ones might try to manipulate the demigods for their own ends.
Percy would likely be very curious about the characters in the Overlord world. He might approach them with his usual friendly and adventurous attitude. The Overlord characters, depending on their nature, could either be hostile or intrigued. For example, the more powerful and evil - inclined characters might see Percy as a threat and try to eliminate him. But the more neutral or good - hearted ones could be interested in learning about his powers and his world.
Percy would probably be a bit of a wild card to the Order of the Phoenix members. He's used to a different kind of magic and a different set of rules. Harry might be initially suspicious of Percy but also intrigued by his powers. They could start off with a bit of a rivalry as they both try to prove themselves in different ways.
Percy would likely be initially cautious yet intrigued by Rory. He might be in awe of her combat skills and the way she commands in battle. Rory, on the other hand, would be curious about Percy's powers related to the sea and his connection to the Greek gods. They would probably start by exchanging stories about their respective worlds and gradually build a bond based on mutual respect and the need to face common threats.
The two could have some really interesting conversations. Percy could talk about his adventures with Annabeth and the other demigods, while Jacob could share stories about his pack and his experiences in the forest. They might also compare their different kinds of powers. Percy's control over water and his ability to withstand a lot of physical damage compared to Jacob's enhanced senses and super - strength as a werewolf. And they could learn from each other. Percy could teach Jacob some Greek, and Jacob could show Percy how to track better in the wild.