--- title: "Pokémon episode ‘Dennō Senshi Porygon’ aired once in Japan in 1997 and sent 685 viewers to hospitals" url: https://badiyaa.com/pokemon-denno-senshi-porygon-episode-1997/ published: 2026-11-15T12:24:00+00:00 modified: 2026-11-15T12:24:00+00:00 section: Gaming publisher: Badiyaa --- # Pokémon episode ‘Dennō Senshi Porygon’ aired once in Japan in 1997 and sent 685 viewers to hospitals Pokémon's 'Dennō Senshi Porygon' aired once on TV Tokyo on December 16, 1997; flashing lights sent 685 viewers to hospitals and it never aired again. One episode of the Pokémon anime has been broadcast exactly once. “Dennō Senshi Porygon,” or “Computer Warrior Porygon,” went out on TV Tokyo at 6:30 p.m. on Tuesday, December 16, 1997, and a four-second burst of flashing red and blue light near its end sent 685 viewers across Japan to hospitals by ambulance. Japan’s press named the night the “Pokémon Shock.” The episode, the 38th of the first season, was top of its time slot with roughly 4.6 million households watching. It has never aired again, in Japan or anywhere else. ## What was on screen The plot is a cyberspace caper. Ash, Misty and Brock shrink into a Pokémon Center’s computer network to stop Team Rocket, who are using a stolen Porygon, a digital Pokémon, to steal other trainers’ Pokémon. An antivirus program fires “cyber missiles” at everyone, and Pikachu answers with a Thunderbolt that causes a huge explosion. That explosion is the problem scene. It aired at 6:51:34 p.m. on 37 stations. Animators used two techniques, known as paka-paka and “flash,” to alternate colors on every single frame. At 24 frames per second, each color flickered 12 times a second, and the longest run lasted four seconds. General director Kunihiko Yuyama later explained the color choice: “We used red and blue flashing for all the explosions inside our cyber space, because we wanted to give the explosions an electrical feel.” ## The night in numbers A survey by Japan’s Fire and Disaster Management Agency counted 685 people, 310 male and 375 female, taken to hospitals; 208 were admitted. Most were of middle and high school age. Many thousands more children reported milder effects at home, though later research suggested many of those milder cases looked more like mass hysteria than seizures. Kanagawa and Osaka each recorded 76 hospital cases, the most of any prefecture, with Tokyo close behind at 74. ## A timeline of the fallout - **December 17, 1997:** TV Tokyo apologized and suspended the show. Nintendo shares fell 400 yen to 12,200 yen on the Tokyo Stock Exchange. Nintendo president Hiroshi Yamauchi said the company was not responsible, pointing out that the Game Boy game was black and white. - **December 23, 1997:** the next planned episode, “Holiday Hi-Jynx,” was pulled; it did not air until October 1998. - **January 1998:** ShoPro began in-person talks with Nintendo of America on a US license, and the American distributor promised to remove flashing effects. - **April 16, 1998:** the anime returned after a nearly four-month break, moved from Tuesdays to Thursdays, preceded by a special program reviewing what went wrong. - **September 1998:** Pokémon premiered in the United States, without this episode. The longer-lasting result was a set of Japanese broadcast rules. Under the guidelines drawn up after the incident, flashing images, especially red ones, should not flicker faster than three times per second, and flashing should not run for more than two seconds in total. Broadcasters also added on-screen reminders on children’s shows to watch in a well-lit room from a distance. ## Why Porygon took the blame The odd twist is that Pikachu’s attack caused the flash, yet Porygon is the one that vanished from the show. Neither Porygon nor its later evolutions, Porygon2 and Porygon-Z, has appeared in another episode, although Porygon still turns up in the games, manga and merchandise. In September 2020 an official Pokémon social account posted “Porygon did nothing wrong,” then deleted it soon after. For more on Nintendo’s history, Badiyaa has covered [why Eiji Aonuma held back on scary ReDeads in the Ocarina of Time remake](https://badiyaa.com/ocarina-of-time-remake-redead-scary-aonuma/) and [the end of Google and Apple sign-ins for Nintendo Accounts](https://badiyaa.com/nintendo-account-google-apple-sign-in-ending/); more stories sit on our [Gaming page](https://badiyaa.com/category/gaming/). The episode’s 29th anniversary falls on December 16, 2026. ## Further reading - [Wikipedia: Dennō Senshi Porygon](https://en.wikipedia.org/wiki/Denn%C5%8D_Senshi_Porygon) *Image: Suicasmo, CC BY-SA 4.0 via Wikimedia Commons* *This article was produced with AI assistance and reviewed by our Editorial Desk. [How we work](https://badiyaa.com/editorial-policy/).*