From Bulbapedia, the community-driven Pokémon encyclopedia.
"Electric Hero Porygon" is also known as "Electric Soldier Porygon". It is a somewhat notorious episode of the Pokémon Anime, due to the fact that on its single airing in Japan, 1997, more than 700 Japanese children suffered seizures, vomiting, irritated eyes and other symptoms.
The episode was never commercially released, even in Japan, nor was it ever re-shown or aired at all in the US.
The scene which caused the seizures was a 15 second section in which Pikachu uses an Electric attack on some vaccine missiles. The explosion was shown as a bright flashing object which alternated rapidly between red and blue.
The seizures caused by this episode caused Toei to drop the strobe effects from Pikachu's electric attacks. Also, a disclaimer to be placed at the beginning of video releases warning about possible seizure-inducing moments, despite the strobe effects already being gone.
Ash and friends find at the local Pokémon center that there is something wrong the Pokéball transmitting devise. To find out what's wrong, everyone must go inside the machine.
- This episode aired (in Japan) between "Ditto's Mysterious Mansion" and "Pikachu's Goodbye".
- The seizures caused from this episode were used by the Simpsons in the episode "30 Minutes Over Tokyo."
- There was originally going to be a New Year's Eve Episode of Pokemon. It was never shown, not even in Japan. Electric Hero Porygon caused this.
- 4 Kids Entertainment have dubbed this episode and reduced the speed and intensity of the flashing explosion to make it safe, but the episode has still never been shown.