Magnemite

Magnemite uses anti-gravity to stay suspended and it usually appears without warning. In "Sparks Fly for Magnemite," Pikachu is diagnosed with a Pokemon cold by Nurse Joy, right before a blackout occurs. Ash and company go exploring through the darkness of the overloaded power plant, and a legion of Magnemite converge upon our heroes — especially the over-electrified Pikachu!

First appearance: Episode 30—"Sparks Fly for Magnemite"