Pikachu, as a Kakuna, looked like any other Kakuna, often being dragged along by Rusty on a leash. As a Beedrill, he is often seen holding a gun with no ammo, but still trying to fire it. He eventually starts wearing a suit after killing Giovanni and taking over Team Rocket.
As a Kakuna, Pikachu was very passive of many of Rusty's unintentional tortures, but he desperatly wanted to get away from Rusty, as displayed when he "evolves out of pure happiness" when a Team Rocket member touches him in an attempt to steal him. As a Beedrill, Pikachu is very aggressive and very violent, killing people without remorse. He is very vengeful against Rusty and has tried to kill him multiple times.
The Pokemon began life without the nickname "Pikachu" and presumably as a Weedle who eventually evolved into a Kakuna at some unknown point in time.
It is unknown when he evolved from a Weedle into a Kakuna. As a Kakuna, he came into the possession of Professor Tree, who mistook the Pokemon for a paper weight. He resided in Professor Tree's lab sitting on the back table, presumably holding down papers during his stay there.
Ownership Under RustyEdit
Professor Tree let Rusty take the Kakuna as his first Pokemon the day Rusty went out into the world. Rusty would transport Pikachu via a blue leash, dragging him along the ground. At some unknown point, Rusty tried to evolve Pikachu by throwing rocks at him, hoping one of them was a Sun Stone. This contributed to Pikachu's growing resentment towards Rusty. Rusty chose a rival and sent Pikachu to battle him. Rusty launched Pikachu at his rival's Rattata, causing it head trauma. When Rusty accidentally captures himself inside a pokeball while trying to catch a Shiny Bidoof, he asks Pikachu to get help, but being a Kakuna, can do nothing.
Later in a cave, Rusty and Pikachu are attacked by Team Rocket. Rusty willingly gives up all of his pokemon except for Pikachu. however, when the Team Rocket member goes to steal Pikachu, he evolves into a Beedrill "Out of pure happiness." Rusty thinks that Pikachu evolved to save him, but Pikachu punches him and flees to the female Team Rocket member and leaves with her to burn down a hospital.
Ownership Under Team Rocket Edit
It is assumed during this time that Pikachu stays at Team Rocket HQ. Team Rocket knows that Pikachu is one of the most psychotic pokemon they have ever had, so it is possible that they keep him there. When Rusty entered the HQ, Pikachu grabbed a gun and shot him out of revenge, but missed him until he was run out of ammo. Team Rocket members let Rusty join when they realized that he was a black-hearted trainer and that he brought drugs withhis bike.
Pikachu continuously pulled the trigger without an ammo while Rusty was assigned to steal a Pokemon via truck. When they met Red, Red unleashed his Charizard to burn down the truck, followed by Magneton and Gyarados to kill the Team Rocket. Rusty claimed that Pikachu was dead.
As The Boss Edit
Pikachu survived the explosion when it couldn't kill him, and his "rage burns brighter than any flame." He entered the Team Rocket HQ and murdered its leader in order to lead the Team Rocket. He resided in the gym on Viridian City. Ruthlessly, he also executed Battle Blart who burned down Battlehaus with Rusty due to having a high debt.
When Rusty told him to get inside the Pokeball, he ordered the Team Rocket member to kill him. However, the police intervened and arrested Pikachu, but Rusty exclaimed that Pikachu was his Pokemon, causing them to turn against Rusty instead. Pikachu expressed a smug when the police tasered his former trainer.