Jolteon

Jolteon is an Eevee that has been exposed to a Thunder Stone. It accumulates negative ions in the atmosphere to blast out 10,000-volt lightning bolts. The second of Michael's brothers in "The Battling Eevee Brothers" tries to get him to use a Thunder Stone on Eevee. He even tries to give Ash the Thunder Stone to make Pikachu into Raichu! Team Rocket, however, just wants to steal the stones and sell them!

First appearance: Episode 40 — "The Battling Eevee Brothers"