He could be in awe at first. I mean, they are gods after all. But then he might start challenging them in a friendly way, like he did with some of the Greek gods. He might show off his water - controlling powers to impress them.
He'd probably be cautious at first. Given his experiences with the Greek gods, he'd know that gods can be unpredictable. He might start by observing the Celtic gods' behavior. Maybe he'd try to find common ground, like their connection to nature or their role in the cosmos.
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.
I think it would be Magnus Chase. Since Magnus has experience with the Norse world and Percy is used to dealing with the demigod stuff, they could combine their knowledge and skills. Also, they both have a sense of justice and would likely work well together.
Percy would interact in a cautious yet curious way. He'd be curious about their powers, like Anubis' role in the afterlife. But he'd also be cautious as he doesn't know how they'll react to a Greek demigod. He might use his charm, which has worked on some Greek gods, to try and build relationships. However, he may face some resistance from the more xenophobic Egyptian gods who see him as an intruder.
Percy would probably be curious about Katara's water - bending. He might ask her to show him some cool moves. Katara, on the other hand, would be interested in Percy's ability to control water in a different way. They would likely start off a bit cautious but quickly become friends as they realize they both have a strong connection to water.
In a fanfiction, Percy Jackson and the Avengers' interaction would be complex. Percy comes from a world of gods and monsters, and the Avengers from a world of super - science. At first, there could be misunderstandings. Percy might think the Avengers are too full of themselves, and they might think he's a bit of a wild card. However, as they face challenges together, like a group of mythical beasts invading New York, they'd learn to rely on each other. Percy could use his ability to communicate with sea creatures to gather intelligence, while the Avengers use their powers to fight on land. Their combined efforts would make them a formidable team.
Percy would probably be in awe of Aquaman's pure Atlantean powers at first. He might be a bit jealous as well, since he's just a demigod with limited underwater abilities compared to Aquaman. Aquaman, on the other hand, would be curious about Percy's connection to the Greek gods. They would start off a bit cautious around each other, but as they face common threats in the ocean, like pirates using dark magic or sea creatures gone berserk, they would gradually start to trust and rely on each other.
Percy could use his skills in combat and his powers over water to interact with dinosaurs. For example, if a dinosaur attacks him near a water source, he could create a large wave to knock it back or use the water to make himself move faster to avoid its attacks. He might also try to communicate with them if he discovers some kind of ancient magic or power that allows him to do so.
Azula would probably try to use Percy at first. She might see his powers as something she could control or use for her own gain. However, Percy is not one to be easily manipulated. He would resist her attempts, which could lead to some intense verbal sparring between them. As time goes on, they might develop a grudging respect for each other. For example, Percy might admire Azula's strategic mind, and Azula could respect Percy's loyalty to his friends.