Porygon was featured in the Pokémon episode known as “Dennō Senshi Porygon.”
The episode aired in Japan on December 16, 1997, as part of the original Pokémon animated series. Its story sent Ash, Pikachu, and their friends into a computer system, where they encountered the artificial Pokémon Porygon and a digital security problem.
The broadcast became infamous because rapidly flashing red and blue light sequences were associated with illness among some viewers. Japanese broadcasters and Pokémon’s producers responded by withdrawing the episode from further television circulation, and it has not received a regular international broadcast release.
Porygon itself was not the source of the visual effect, but its name became attached to the episode because it is central to the plot and title. The incident also led to changes in production practices for animated television programs.