Pokémon HeartGold Version Unlockables

In-game trades
Throughout your journey you may come across trainers who are willing to trade their Pokemon for yours. The Pokemon they offer you will usually be holding a valuable item, or may even know a special attack!

The chart below shows which Pokemon the trainers in the game are looking to trade, as well as the Pokemon you will need to offer in return:
UnlockableHow to unlock
Onix (Holding Persim Berry)Trade Bellsprout to the man in Violet City
Machop (Holding Macho Brace)Trade Drowzee to the gentleman located inside of the Goldenrod Dept. Store
Voltorb (Holding Cheri Berry)Trade Krabby to the fisherman in Olivine City
Dodrio (Holding Smoke Ball)Trade a female Dragonair to the woman in Blackthorn City
Xatu (Holding Wacan Berry)Trade a Haunter to the man located inside of the Pewter City Pokemon Center
Magneton (Holding Metal Coat)Trade a Dugtrio to the scientist located inside of the Power Plant
Pikachu (Holding Yellow Shard)After defeating Lt. Surge a second time, speak with him in the Saffron City Magnet Train Station -he'll request a Pikachu caught in Viridian Forest for his own
Beldum (Holding Dawn Stone)Speak with Steven in the Silph Co. Lobby, after obtaining the Hoenn starter from him and having spoken to him in the Pewter City Museum
Rhyhorn (Holding Passho Berry)After defeating Brock, he will request a Bonsly in exchange for his Pokemon
Steelix (Holding Soothe Bell)After defeating Jasmine a second time, she will call you on your phone and request a trade for any of your Pokemon