In Pokémon Gold, Silver, and Crystal there are two different types of terrain. Which has an affect on where pokémon that fall out of trees by using TM02 Headbutt. The two types of terrains are Forest terrain and Mountain terrain. Here are a is of pokémon unique to the terrain:
| Pokémon: | Rarity: | Terrain: | Versions: |
| Caterpie | Common | Forest | Gold |
| Metapod | Uncommon | Forest | Gold |
| Butterfree | Rare | Forest | Gold |
| Weedle | Common | Forest | Silver |
| Kakuna | Uncommon | Forest | Silver |
| Beedrill | Rare | Forest | Silver |
| Exeggcute | Uncommon | Forest | Gold, Silver, and Crystal |
| Pineco | Rare | Forest | Gold, Silver, and Crystal |
| Aipom | Super Rare | Mountain | Gold, Silver, and Crystal |
| Heracross | Super Rare | Mountain | Gold, Silver, and Crystal |
| Spearow | Common | Mountain | Gold, Silver, and Crystal |
Now that you know what terrain which pokémon hide in, you need to know where the terrains are. The forest terrain is located on routes 26-41 while the mountain terrain is late in the game on routes 42-45.
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