Cress, Cilan, and Chili were apprentices under Siebold. He taught them most of what they know today, in both battling and cuisine. He stops by their restaurant every once in a while. (anon)
When they were young, Professor Oak, Agatha, and Kurt were all competitive trainers and battled each other on occasion like the player characters and rivals. The Bulbasaur, Charmander, and Squirtle that Oak offers Red and Green (and Blue) are the offspring of Oak’s Charizard, Agatha’s Venusaur, and Kurt’s Blastoise. But they grew apart when Sammy wanted to study Pokemon, Kurt mastered the craft of making Pokeballs, and Agatha stayed a competitive trainer. (anon)
It is considered Pokemon abuse to use Pokemon for power or water without a permit (ex. using a Pikachu to charge your laptop) (anon)
N, Cheren, Bianca, and Hilda found a small theatre group in Opelucid. They decided to try it out, and now love participating in the plays. (Anon)
Beautifly, Butterfree, and Dustox all used to be the same species, but were separated by the tectonic plates shifting. Once the Hoenn descendants were separated, one half coexisted with humans and became Dustox while the others evolved completely in nature, becoming Beautifly. To this day, they’re cross-bred to try and create a Buterfree-like Pokemon for the Hoenn region. (rex-l-ligdraer)
The reason that Arceus is worshiped as a god is because Sinnoh has been befallen by many disasters which Arceus has stopped. In fact, Arceus has fought and defeated every type of hostile Pokemon in Sinnoh. The reason it doesn’t interfere anymore is because Arceus lost its plates after fighting Palkia, Dialga, and Giratina at the same time; losing most of its incredible abilities. (rex-l-ligdraer)
In Sinnoh there is an unspoken taboo against tampering with Celebi’s powers in any way, which Grings Kodai did not know about because he was from Unova originally. (alchan)
Siebold has difficulty holding a chef job due to his temper, despite having great skill. (blackjackgabbiani)

Jupiter started out studying medicine but left in dismay when she found that her classmates were in it for the money. She began to doubt the entire idea of compassion, and joined Team Galactic because of their aim of duty and justice for the world without compassion. (blackjackgabbiani)

After the events of G, S, C, HG and SS, Silver found a lost man in the Ilex forest. He decided to help him anyway and the man felt bad for Silver when he heard his story. The man payed for his education, a house and food. Silver still thought that the world was filled with horrible people and was ashamed that he used to be a part of them. Silver wanted to return the favor to join team Flare. Lysandre refused in the beginning, but he him join as a higher ranked member of team flare. (anon)