Aerodactyl - Revive the Old Amber Fossil.
- You get Old Amber by randomly smashing rocks in the Ruins of Alph.
Kabutops - Revive the Dome Fossil.
- You get Dome Fossil by randomly smashing rocks in the Ruins of Alph.
Omastar - Revive the Helix Fossil. (Exclusive to HeartGold).
- You get Helix Fossil by randomly smashing rocks in the Ruins of Alph.
Porygon - Purchase at the Celadon Game Corner for 9,999 Coins.
- You can get as many as you want.
Porygon 2 - Evolve Porygon.
Phanpy - Johto Route 45, Mt. Silver (Exclusive to HeartGold).
- Trade one over to SoulSilver.
Smoochum - Catch in PokeWalker (Dim Cave & Amity Meadow).
- You can also breed a Jynx (Caught at Seafoam Islands & Ice Path).
Octillery - Evolve Remoraid.
- Remoraid can be caught at Johto Route 44 during a Swarm.
Mantine - Route 41 (Exclusive to HeartGold).
Gligar - Route 45 (Exclusive to HeartGold).