The cow called Boy might have adventures like exploring new pastures that he wasn't allowed in before. Maybe he found a hidden stream and had a great time drinking from it.
There could be many possible stories about a cow called Boy. Maybe Boy was a very special cow on a farm. It could be the friendliest cow, always approaching the farmers for pats and treats. Or perhaps Boy was the bravest cow, protecting the other cows from some sort of danger on the farm.
It could be a tale of how the cow called Boy overcomes challenges, makes friends, or discovers something special. Or perhaps it's a simple story of Boy's peaceful existence in a rural setting.
Wally and Kuki are likely characters in a particular fictional universe. They could be from a TV show, a video game, or a comic. Without more context, it's hard to say exactly who they are, but they are the focus of the fanfiction, which means fans are interested in exploring their relationship, be it friendship, romance, or some other kind of connection.
It could be a fantasy tale where some magical or strange event causes the boy to transform into a cow. Maybe it has elements of adventure and self-discovery.
A best cow story usually has a cow with unique qualities. For example, if the cow is very kind to other animals or helpful to the farmer. If it can do something extraordinary like saving another animal from danger or finding a great source of food, that makes it a great story.
It could be a tale about a boy's special bond with the cow or a part of a larger myth involving some sort of task or challenge related to the daily cow-picking.