How do you get Deoxys Mew and Celebi in Pokemon heart gold?

Answer 1

Before I go on, I'd like to say that without a Cheating Device, you cannot get these Pokemon from HeartGold.

Deoxys - Migrate from the GameBoy Pokemon Cartridges to Pokemon Pearl or Diamond by using the Pal Park. Afterwards, trade Deoxys to HeartGold or SoulSilver. (By the way, Deoxys can be found at Birth Island in the GameBoy Pokemon Cartridges.)

Mew - It seems that Emerald is the only GameBoy Pokemon Cartridge that has Mew. Migrate Mew to Pokemon Pearl or Diamond, like Deoxys, and trade it to HeartGold or SoulSilver. (Mew can be found at Faraway Island in Emerald.)

Celebi - Migrate from the GameBoy Pokemon Cartridges to Pokemon Pearl or Diamond by the Pal Park. Do the same with the others and trade Celebi to HeartGold or SoulSilver. (Nintendo Event is needed for this lovely Legendary.)