Strobe lights

Twenty minutes into the episode, Pikachu stops missiles with his Thunderbolt attack, resulting in an explosion that flashes red and blue lights.^[1][5] Although there were similar parts in the episode with red and blue flashes, two anime techniques, called "paka paka"^{[lower-alpha 1]} and "flash",^{[lower-alpha 2]} made the scene particularly intense.^[2] These flashes were bright strobe lights, with blinks at a rate of about 12 Hz for approximately six seconds.^[6]

At this point, some of the viewers experienced blurred vision, headaches, dizziness and nausea.^[1][5][7] Some suffered seizures, blindness, convulsions and unconsciousness.^[1][5] Japan's Fire Defense Agency reported that 685 viewers – 310 boys and 375 girls – were taken to hospitals by ambulances.^[5][8] Although many victims recovered during the ambulance trip, more than 150 were admitted to hospitals.^[5][8] Two were hospitalized for more than two weeks.^[8] The incident was referred to as "Pokémon Shock" (ポケモンショック, Pokémon Shokku) by the Japanese press.^[9]

Later studies showed that 5–10% of the viewers had mild symptoms that did not need hospital treatment.^[6] Twelve thousand children who were not sent to hospital reported mild symptoms of illness; however, their symptoms more closely resembled mass hysteria than a seizure.^[5][10][11] A study following 103 patients over three years after the event found that most had no further seizures.^[12] Although approximately 1 in 4,000 people are susceptible to these types of seizures, the number of people affected by the Pokémon episode was unprecedented.^[1][8]

Immediate response

To prevent any similar incidents from occurring, the episode was pulled from rotation, and it has not aired since in any country.^[1]

The following day, the television station that had originated the lone broadcast of that episode, TV Tokyo, issued an apology to the Japanese public, suspended the program, and said it would investigate the cause of the seizures.^[5] Numerous video retailers across Japan removed the Pokémon anime from their rental shelves in response to the incidents.^[5]

Officers from Atago police stations were ordered by Japan's National Police Agency to question the anime's producers about the show's contents and production process.^[2]

On the Tokyo Stock Exchange, shares in Nintendo (the company that publishes the games that the anime is based on) fell by 400 yen the following morning to 12,200 yen (almost 3.2%).^[5][13] The president of Nintendo, Hiroshi Yamauchi, said at a press conference the day after the episode had aired that the video game company was not responsible since the original Pokémon game for its Game Boy product was presented in black and white.^[13]

Effect on the Pokémon anime

After the airing of "Dennō Senshi Porygon", the Pokémon anime went into a nearly four-month hiatus.^[1][14]

The episode "Rougela's Christmas" ("Holiday Hi-Jynx"), which would have aired the following week, December 23, 1997, was pulled following the incident, and would not air until October 5, 1998. Airing out of order caused confusion to viewers because Ash still had a Charmander instead of Charizard, and Misty did not have Togepi yet, but Starmie and Horsea. Also, a New Year special that would have aired on December 30, 1997, was pulled and never resurfaced.^{[citation needed]}

All 37 episodes of Pokémon: Indigo League were rerun on Kids Station in Tokyo leading up to the show's return on April 16, 1998, with airing of "Forest of Pikachu" ("Pikachu's Goodbye") and "The Four Eevee Brothers" ("The Battling Eevee Brothers").^[14][15] After the hiatus, the time slot changed from Tuesday to Thursday.^[3]

Before broadcasting resumed, the special program "Problem Inspection Report on the Pocket Monsters Anime" (アニメ ポケットモンスター問題検証報告, Anime Poketto Monsutā Mondai Kenshō Hōkoku) was shown. Broadcast in Japan on April 16, 1998, host Miyuki Yadama went over the circumstances of the program format and the on-screen advisories at the beginning of animated programs, as well as showing letters and fan drawings sent in by viewers, most of whom were concerned that the incident would lead to the anime being cancelled.^[3]

"Dennō Senshi Porygon" itself has never been aired again, in any country.^[1] The Pokémon anime has not featured Porygon or its evolutions, Porygon2 and Porygon-Z, in any subsequent episodes outside of brief cameos, despite Pikachu being the one to cause the seizure-inducing strobe effect.^[16]

Changes to television standards

Many Japanese television broadcasters and medical officials (along with the United Kingdom's Independent Television Commission^[21]) came together to find ways to make sure the incident was not repeated. They established a series of guidelines for future animated programs,^[8][22] including that flashing images, especially those with red, should not flicker faster than three times per second; if the image does not have red, it still should not flicker faster than five times per second; flashing images should not be displayed for a total duration of more than two seconds; and stripes, whirls and concentric circles should not take up a large part of the television screen. The Harding test for content that now airs on Japanese TV and streaming sites ensures no more than one flashing light occurs every 10 frames, reproduced at 29.97 FPS, where "flashing lights" are classified as extreme changes in colors from one frame to the next. Footage may either clear or fail checks, or "pass with a warning" in which case the video's luminance is automatically adjusted to mitigate potential effects.^{[citation needed]}

After the incident, TV broadcasters voluntarily added on-screen warnings to shows targeted at young children encouraging viewers to watch anime in a well-lit room and to sit far away from the television set.^[23]