He could meet his future self. It would be an interesting encounter as he could learn from his future experiences and wisdom. Or he might meet people who have studied his past adventures and see himself through their eyes.
Possibly they are random villagers who were caught in the crossfire of a conflict between different bending factions. Aang, being the Avatar and a symbol of peace, feels responsible for burying them and ensuring their spirits are at peace.
He might start by observing. Aang is a curious person, so he'd likely watch how people live, how they interact with technology. He may also try to find other benders to learn about any new developments in bending. And he'd probably use his kind heart to make friends easily in this new future environment.
One possible fanfiction could be about Ash training really hard in a special region where he discovers a new type of Pokemon that has a unique energy. This energy somehow affects his physical development, making him muscular. He then uses his newfound strength to overcome tougher challenges in battles.
In the wide world of fanfiction, 'Muscular Bull Anthro' is a theme that exists but is not overly prevalent. There are a few reasons for this. First, it caters to a specific taste. Those who like this theme are often interested in the combination of the animalistic features of a bull with a human - like form, especially a muscular one. It can be used to create interesting power dynamics within a story, whether it's in a fantasy setting where the bull anthro is a warrior or in a more modern - day - inspired story where they are just an unusual character in an urban environment. But because it's not a theme that appeals to the general masses, it remains somewhat of a niche concept within the fanfiction universe.
The theme of adaptation is also prevalent. Having a muscular body means Percy has to adapt to new abilities and limitations. His center of gravity might change, or he might have to learn new fighting techniques. Fanfictions often explore how he copes with these changes in his day - to - day life and in battles.
Sokka could be one of the main characters. He might be the one helping Aang with his schoolwork, especially in subjects like history or math, using his own knowledge and quick thinking.
Aang might go into a deep state of depression. He has always been an emotional character, and having his heart broken by Katara, someone he loves deeply, could send him into a downward spiral. He might isolate himself from his friends and stop practicing his bending for a while.
In some fanfictions, Aang's connection to his past lives plays a crucial role. He could draw on the wisdom and skills of previous Avatars. They might guide him on how to defeat Azula specifically. He could learn a new bending technique from one of his past lives that gives him an edge over Azula's firebending, like a unique way of using water to extinguish her most powerful fire blasts.