Which Pokémon anime episode caused the 1997 broadcast incident in Japan?

“Dennō Senshi Porygon” caused the 1997 Pokémon broadcast incident in Japan.

The episode aired on 16 December 1997. A sequence involving rapidly alternating red and blue flashes was followed by reports of health symptoms among some viewers, including dizziness, headaches, and seizures. Hundreds of people were taken to hospitals or examined after the broadcast.

The incident led TV Tokyo to suspend the Pokémon anime temporarily while broadcasters and producers reviewed the episode. “Dennō Senshi Porygon” was not rebroadcast in Japan, and Porygon and its evolutionary family were largely absent from later anime appearances for many years.

The event also changed animation-broadcast safety practices. Later Pokémon episodes used restrictions on flashing effects, including limits on brightness and frequency. The incident is sometimes incorrectly attributed to Pikachu because Pikachu appears in the scene, but the episode title specifically refers to Porygon.