One way is to put them in situations where they have to rely on each other's strengths. If Percy is in a place where his water powers are useless, Thalia's lightning and combat skills can save the day, and vice versa. Also, they could have inside jokes and memories that are unique to them. Maybe they create a secret handshake or a special code word. Another aspect is to show them growing together, like learning new skills from each other. Thalia could teach Percy some wilderness survival skills, and Percy could show Thalia some new combat moves he learned from another camper. All these things would strengthen their bond as best friends.
Thalia could be developed by showing her struggle with the weight of the prophecy. For example, she might have nightmares about it, which would make her more vulnerable and human. This would also add depth to her character as she tries to hide her fears from others while still being a strong leader.
They could go on a quest together. During the quest, they face hardships like running out of food or being chased by monsters. Through these shared experiences, their bond can strengthen. For example, Percy could save Grover and Juniper from a monster attack, and they would be more grateful and closer to him.
In fanfiction, they could face a big crisis together, like a major bridge collapse that blocks the railway. As they work side by side to fix the problem and keep the railway running, their bond of friendship would grow stronger. They might have to rely on each other's unique skills, with Thomas being fast and Edward being strong.
Imagine Percy and Annabeth get sent on a diplomatic mission to another demigod camp. They have to work together to convince the other camp to form an alliance. Along the way, they face many challenges, not just from the other camp but also from within themselves as they have different ideas on how to approach the situation. Through this experience, they learn to communicate better, trust each other more, and their friendship reaches a new level.
They could go through a really tough trial together. For example, they are trapped in a maze - like place full of dangerous traps and monsters. In this situation, they have to rely on each other completely. Grover uses his knowledge of nature to find hidden paths, and Percy uses his combat skills to protect them. This shared experience would deepen their bond.
Their friendship can be developed by having them share their deepest secrets. For example, Max could tell Eleven about her family issues, and Eleven could open up about her past in the lab. This would create a stronger bond between them.
By showing them having heart - to - heart conversations. For example, Percy could share his fears about his powers with Thalia, and she could offer her own experiences and advice.
They could face a really tough situation together, like being stuck in a game world where they have no powers. They'd have to rely on each other's wits and personalities. Ralph could use his big - heartedness and Vanellope her cleverness to get out. This would deepen their bond as they see new sides of each other.
One way is by having them go through a really tough trial together, like being wrongly accused of a crime in Auradon. They would have to prove their innocence and during this process, they would rely on their trust in each other. Their friendship would deepen as they see how far they are willing to go for one another.
By showing them having heart - to - heart conversations. For example, they could talk about their experiences growing up as demigods, their fears, and their hopes. This would deepen their connection.