James' Weezing one of James's Pokémon. He got him for Christmas as a Koffing. During the Kanto Region it became James's Main Battling Pokémon. It was often used by James, some times Jessie, as well as Team Rocket's get away by using either Smog or Smokescreen. It evolved from Koffing in the episode Dig Those Diglett at the same time Jessie's Ekans evolved into Arbok.
His Weezing helped James capture and defeat Victreebel when it was a Weepinbell in a flashback.
James had to release his Weezing along with Jessie (who had to release Arbok) to save a group of Koffing and Ekans. They strongly cried when they did. Nothing is known of Weezing or Arbok now. They are presumed to still be with the Koffing and Ekans to this day.
Weezing as a Koffing
Weezing and Arbok crying
Weezing and Arbok with Jessie and James
Weezing and Arbok leaving Jessie and James forever