The Pokémon anime episode associated with the 1997 flashing-light incident was episode 38.
Titled “Dennō Senshi Porygon,” or “Computer Warrior Porygon,” it aired only once in Japan, on December 16, 1997. A sequence near the end used rapidly alternating red and blue flashes during an explosion, after which many viewers reported symptoms including dizziness, nausea, and seizures.
More than 600 people were taken to hospitals, according to contemporary accounts. The incident led to the Pokémon anime entering a hiatus of nearly four months. The episode was removed from rotation and has not been broadcast again in any country.
Although Porygon gives the episode its title, Pikachu’s Thunderbolt creates the flashing explosion in the scene commonly associated with the incident. Porygon and its evolutions subsequently disappeared from later Pokémon anime episodes, even though Pikachu remained a central character.