A December 1997 episode of the Pokémon anime triggered photosensitive seizures in approximately 685 Japanese children, resulting in the temporary suspension of the series and new broadcast guidelines across Japanese television.
The offending sequence in episode 38 was produced by animation director Yūji Asada and involved a deliberate stylistic choice to represent a computer-world explosion through high-frequency strobe effects. The red-blue alternation occurred at approximately twelve flashes per second — well within the range known to trigger photosensitive episodes. The animators were not unaware of photosensitivity as a medical condition but apparently did not apply the precautionary standards that would have prevented the sequence from being broadcast. The episode aired at 6:30 PM on a Tuesday, during a period of high viewership among its primary demographic of children under twelve.
The response in Japan was immediate and extensive. Ambulances were called across multiple cities within minutes of the broadcast; hospitals in the Tokyo area reported clusters of paediatric seizure cases arriving simultaneously. The number of affected viewers — 685 seeking medical treatment, with a larger number experiencing milder symptoms — was unprecedented for a broadcast event and attracted international press coverage, including in outlets that had not previously covered the Pokémon franchise.
TV Tokyo's suspension of the Pokémon anime was immediate — the network pulled the series the following week and did not return it to broadcast for four months. When the anime resumed in April 1998, it did so with a visible disclaimer before each episode advising viewers to watch in a lit room, at a distance from the screen, and to stop watching if they felt unwell. Nintendo and the Pokémon production companies issued formal apologies. The episode itself was never rebroadcast in Japan and was not included in home video releases, effectively quarantining it from the official Pokémon catalogue.
The Broadcasting Ethics and Program Improvement Organisation (BPO) in Japan conducted a review of the incident and issued guidelines that subsequently applied to all broadcast television, not only animation. These guidelines specified maximum flash frequencies, contrast ratios, and proportions of screen area that could be occupied by high-contrast patterns — standards that were later adopted in modified form by broadcasters in other countries, including the UK's Ofcom guidelines on photosensitive epilepsy.
The episode's title character, Porygon — a virtual Pokémon that existed as a computer programme — was effectively banned from the anime despite having played no role in the offensive animation. The flashing sequence was caused by Pikachu's electric attack, not by Porygon, but the episode's association with the incident made producers unwilling to feature the character in any subsequent episode. Porygon received two evolved forms in later games — Porygon2 and Porygon-Z — but neither evolution ever appeared in an action sequence in the anime. This outcome became something of a dark joke within the Pokémon fan community: the one character punished for the incident was the one character that had done nothing wrong.
Japanese television broadcasters adopted new guidelines restricting the use of rapidly alternating high-contrast flashing in all programming; the Pokémon anime returned in April 1998 with modified production practices; Porygon never again appeared in an action role in the Pokémon anime.