Denno Senshi Porygon, an episode of Pokemon first aired on December 16, 1997, was the first of its kind. The episode in question was able to send 675 children to hospitals in ambulances due to seizures, nausea and trouble seeing. The reason for these ill effects, were due to a particular scene in the episode. Approximately 20 minutes in to the episode, Pikachu destroys a missile with its thunderbolt attack. The explosion that followed was animated in flashing red and blue lights. The lights in question blinked at 12 Hz for 4 seconds in near full screen, and then another two seconds in full screen. The amount of children affected was unprecedented, and holds a Guinness World Record: "Most Photosensitive Epileptic Seizures Caused by a Television Show". Was this necessary? Why was the episode not tested, before broadcasting? Why did the Japanese Government let this episode through the filter? The answer is clear, they wished for Porygon to be discriminated against.
Let us take a closer look at the facts for a minute. The first episode that Porygon ever appeared in is where the incident occurred. Porygon is a computer Pokemon, which represents progress and change. In the episode, the protagonists end up going into a computer system, where we end up meeting our poor hated Pokemon. The Japanese government wants to control their people as much as possible, and they lose a lot of that control when their citizens gain access to technology. Seeing as how Porygon represents this technology, the Japanese government saw it as a threat, and placed the seizure inducing scenes inside the episode.
There were quite a lot of things to happen after the episode was shown in Japan. Around 12 000 were not sent to hospital, but still had minor symptoms after watching the episode. Nintendo's stocks went down 5%. Japanese television broadcasters also produced a set of guidelines for flashing lights in anime shows. Flashing lights were no longer allowed to flash more than three times per second. The flashing images were also not allowed to be shown for more than two straight seconds. The episode was subsequently banned in every other country that Pokemon is shown, and has yet to be shown. The episode was even dubbed, and had the flashing slowed down. This is what the Japanese government has done. They have stopped progress, by effectively removing one of the Pokemon (and its evolutions) that is on the forefront of change. Porygon, Porygon2 and Porygon-Z have never been shown in the anime, and probably never will.
