Counter works for Special Hidden Power moves (Generations II/III, Generation III version)

This is also called the "Hidden Power glitch". Counter rather than Mirror Move will work to return the damage from an opposing Hidden Power, even if the Hidden Power move was special. This is because apparently Hidden Power is still registered by the game as a Normal-type. This no longer occurs in Generation IV due to the physical/special split by move rather than type where Hidden Power is always special. Note Counter/Mirror Coat do not work if you hit your partner Pokémon in a Double Battle.
I forgot to record this for Generation II. In the future I might upload a separate video for that.

[@CesarTorres61296]

This is actually kind of useful in competitive pokemon. Not much stuff runs Counter, but bulkier mons (like Swampert or Meganium) can get surprise knockouts if they Counter on a Hidden Power.

[@ChickasaurusGL]

Thanks for the info! ^^ Yeah, I heard it was known in competitive circles but didn't know the implications of it.

[@hyoroemongaming569]

I knew it something weird is in code. My Suicune mirror coat my senpai's Kyogre EQ. We were using GBA cable