>>32618846A Pidgeot in Pokemon Yellow.
After realising i cant beat Brock just with Pikachu, i caught a Pidgey and finally succeeded. After that i somehow only used that little bird for everything, until it became my best bro and even reached level 100. Pikachu was even boxed after the third gym.
Then i transfered him to Gold and realised it was female. My bro became my sis.