You can't find a Whismer walking around.
Chat with our AI personalities
Breed a Loudred and hatch the Egg
go to Sandgem town and talk to the girl that says which Pokemon is where
no you can't find a Regigigas in Pokemon Heartgold at all. That person used cheat codes to make a Regigigas appear out of nowhere.
You can find it in Pokemon Platinum, Pokemon Crystal, Pokemon HeartGold, and Pokemon SoulSilver.
Find and then catch