Even more than Porygon, Porygon2 seems to be the most neglected Pokemon of the first three gens, and perhaps even the franchise.
Porygon not only appeared in it's infamous episode (38), but appeared after in two transition scenes in episodes 47 and 69, and appeared in the "Who's that Pokemon?" section of episode 98 in the English dub, meaning it even got an English voice from that appearance. It also got a background appearance in either the 4th or 5th movie, depending on dub or sub.
Porygon2 has never gotten a voice, sub or dub. It's only "appearances" in the anime have been in the English Johto Pokerap and the 15th movie, as just the stock reference art (pic related, left).
For reference, even Porygon-Z got a voice in PokéPark Wii: Pikachu's Adventure.
People say "Porygon did nothing wrong!" and that it was actually Pikachu that triggered all those childrens' epilepsy. I don't necessarily agree with that, since Porygon was still the star of the episode, but Porygon2 genuinely had nothing to do with the incident other than being from the same evolution line. What a waste.
Here's the documentary on the incident for those who haven't seen it, by the way,
https://www.youtube.com/watch?v=DcBvwqhWvFU
I find it fascinating that there even was an anime design reference sheet for Porygon2 in the leaks, when it never appeared. It's actually cool to see how it would have blinked.