If Ash were to find an injured Pokémon with a mysterious ailment that Professor Juniper has never seen before. He brings it to her, and they work day and night to figure out how to heal it. Through this intense and emotional experience of caring for the Pokémon together, their relationship could grow in a unique and deep way.
One way is through a crisis situation. Let's say a powerful and dangerous Pokemon is on the loose. Ash and Professor Juniper have to work together to calm it down. During this process, they learn about each other's strengths and weaknesses. Ash sees Professor Juniper's courage and intelligence in handling the situation, and Professor Juniper admires Ash's determination and connection with Pokemon. This mutual admiration can lead to a stronger relationship.
Another way to develop their relationship uniquely is if Aipom gets a prophecy about a great danger that Ash will face in the future. Aipom decides to secretly train itself extra hard to be able to protect Ash. When Ash finally discovers what Aipom has been doing, he is touched and their relationship becomes even stronger. This would show a different side of their relationship, with Aipom being the protector instead of the one usually being protected by Ash.
Their relationship could develop uniquely if they were forced to take care of a baby Pokemon together. This shared responsibility would make them see each other in a new light and build a bond.
Their relationship could be developed through Pokémon training. For example, Young Nurse Joy has a special Pokémon that she's been having trouble training. Ash offers to help her. As they train together, they learn more about each other's personalities and values. Ash's bold and adventurous spirit rubs off on Nurse Joy, and her kind and nurturing nature makes Ash more empathetic towards his Pokémon.
The relationship could be developed through shared dreams. Maybe Mewtwo has the ability to enter Ash's dreams, and in these dreams, they have adventures together that are different from their real - world experiences. This would create a very special and unique bond between them.
Their relationship could be developed uniquely by having them start as enemies in a sense. For example, Sephiroth could be on a mission that Aerith unknowingly gets in the way of. But instead of killing her immediately, he's intrigued by her. This initial encounter could spark a series of events where they keep crossing paths. Each time, they learn a bit more about each other. Maybe Aerith starts to see the pain behind Sephiroth's cold exterior, and Sephiroth begins to respect Aerith's strength and determination. Over time, this could lead to a complex relationship that is part friendship, part something more, as they both struggle with their own destinies and how the other fits into it.
Their relationship could be developed through a shared love of transfiguration. Hermione could seek out McGonagall for extra lessons and in the process, they bond over the beauty and complexity of the subject.
One way would be if they were both transported to a different dimension. In this strange new place, they have only each other to rely on. They would need to figure out how to survive and find a way back home. This shared struggle would bring out different sides of their personalities and force them to trust each other completely, thus developing their relationship in a very distinct way.
Their relationship could be developed uniquely by having them swap powers for a day. This would force them to understand each other on a whole new level. For instance, Draculaura would have to deal with Clawd's werewolf instincts and Clawd would have to adapt to Draculaura's vampire abilities. It would create a lot of comical and also some very heartfelt moments as they support each other through the challenges.
Their relationship could be developed by having them swap bodies temporarily. This would force them to understand each other on a deeper level as they experience life from the other's perspective. They would then have a newfound respect for each other.