One common theme is the idea of redemption. Since Professor Pester is often a bit of a troublemaker in the game, fanfictions might explore him changing his ways for the reader. Another theme could be adventure, where the reader and Professor Pester go on various quests together in the Viva Pinata world.
Another option could be to check out some Viva Pinata fan communities on social media platforms. For example, on Reddit there might be specific groups dedicated to the game and its fan creations. Members of these groups could potentially share links to or recommend good Professor Pester x Reader fanfictions that they've come across.
Well, the pinata comes from Mexico originally. It was part of the Aztec culture. They created these colorful objects. The Aztecs used pinatas in their own ways, often related to their harvest festivals. When the Spanish conquistadors arrived, they modified the pinata a bit to fit into their new religious context in Mexico. Eventually, it evolved into the fun, candy - filled thing we know today for parties.
I'm not sure specifically which 'girl christmas pinata story' you mean. There could be many different stories involving a girl and a Christmas piñata. Maybe it's about a girl who has a special Christmas where she gets to break a piñata filled with her favorite candies. Without more details, it's hard to tell the exact story.
One key element is the Aztec origin. They started the concept of the pinata as part of their religious and cultural traditions. Another is the influence of the Spanish. Their arrival in Mexico led to changes in the pinata's form and the context in which it was used.