Here's my Pikachu's lore:
This is Pika, partner of my Pokémon oc. During his trip to Kalos, he received a joint attack from the legendary Pokémon Xerneas and Yveltal, which left him in a state of petrification. My oc looked for every means to reverse this effect and never succeeded. The years passed and Pika's body was kept at rest under the tree where it was found by my oc in the Green Forest in the Kanto Region. Five years after the incident my oc decides to return to Kalos in the quest to bring Pika back to life. After the events of Pokémon Legends Z-A, my character asks Zygarde to help him with Pika and he accepts. Pika revives with a somewhat peculiar appearance. He can now sense Zygarde cells near him, and his electricity reacts to them and vice versa, sometimes momentarily giving him power.
by Eatos_w